Practice · Ten in a place carries forward · Sensim Math

Variant 1 easy

There is a three-digit number made up of $4$ hundreds, $15$ tens, and $10$ ones. The number that is $120$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 4 hundreds, 15 tens, and 10 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 120 from it and ask how many tens make up that result.

Givens

The number is 4 hundreds, 15 tens, and 10 ones.
A second number is 120 less than this one.

Unknowns

How many tens make up the number that is 120 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 4 hundreds is 400, 15 tens is 150, and 10 ones is 10. Combine them by carrying the extra tens and ones into the next place.

400 + 150 + 10 = 560

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 120

#7 Identify Subproblems 3.NBT.A.2

Now take 120 away from 560 to get the number that is 120 less.

560 - 120 = 440

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 440 as a count of tens: 440 is 44 groups of ten (with 0 ones left over).

440 = 44 \times 10 + 0

Seeing 440 as 44 tens is just place-value reading.

Answer: 44

4 · Reviewdoes it hold up?

Check: 44 tens = 440, and 440 + 120 = 560, which matches the original number 560, so the work is right.

Another way: Guess and check (Tool 6): a number that is 44 tens is 440; verify 440 + 0 + 120 = 560 matches the description, confirming 44 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 4 hundreds, 15 tens, 10 ones into 560 and re-reading 440 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 560 - 120 = 440 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 2 easy

There is a three-digit number made up of $5$ hundreds, $12$ tens, and $15$ ones. The number that is $130$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 5 hundreds, 12 tens, and 15 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 130 from it and ask how many tens make up that result.

Givens

The number is 5 hundreds, 12 tens, and 15 ones.
A second number is 130 less than this one.

Unknowns

How many tens make up the number that is 130 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 5 hundreds is 500, 12 tens is 120, and 15 ones is 15. Combine them by carrying the extra tens and ones into the next place.

500 + 120 + 15 = 635

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 130

#7 Identify Subproblems 3.NBT.A.2

Now take 130 away from 635 to get the number that is 130 less.

635 - 130 = 505

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 505 as a count of tens: 505 is 50 groups of ten (with 5 ones left over).

505 = 50 \times 10 + 5

Seeing 505 as 50 tens is just place-value reading.

Answer: 50

4 · Reviewdoes it hold up?

Check: 50 tens = 500, and 505 + 130 = 635, which matches the original number 635, so the work is right.

Another way: Guess and check (Tool 6): a number that is 50 tens is 500; verify 500 + 5 + 130 = 635 matches the description, confirming 50 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 5 hundreds, 12 tens, 15 ones into 635 and re-reading 505 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 635 - 130 = 505 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 3 easy

There is a three-digit number made up of $6$ hundreds, $12$ tens, and $16$ ones. The number that is $180$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 6 hundreds, 12 tens, and 16 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 180 from it and ask how many tens make up that result.

Givens

The number is 6 hundreds, 12 tens, and 16 ones.
A second number is 180 less than this one.

Unknowns

How many tens make up the number that is 180 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 6 hundreds is 600, 12 tens is 120, and 16 ones is 16. Combine them by carrying the extra tens and ones into the next place.

600 + 120 + 16 = 736

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 180

#7 Identify Subproblems 3.NBT.A.2

Now take 180 away from 736 to get the number that is 180 less.

736 - 180 = 556

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 556 as a count of tens: 556 is 55 groups of ten (with 6 ones left over).

556 = 55 \times 10 + 6

Seeing 556 as 55 tens is just place-value reading.

Answer: 55

4 · Reviewdoes it hold up?

Check: 55 tens = 550, and 556 + 180 = 736, which matches the original number 736, so the work is right.

Another way: Guess and check (Tool 6): a number that is 55 tens is 550; verify 550 + 6 + 180 = 736 matches the description, confirming 55 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 6 hundreds, 12 tens, 16 ones into 736 and re-reading 556 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 736 - 180 = 556 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 4 medium

There is a three-digit number made up of $3$ hundreds, $18$ tens, and $12$ ones. The number that is $200$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 3 hundreds, 18 tens, and 12 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 200 from it and ask how many tens make up that result.

Givens

The number is 3 hundreds, 18 tens, and 12 ones.
A second number is 200 less than this one.

Unknowns

How many tens make up the number that is 200 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 3 hundreds is 300, 18 tens is 180, and 12 ones is 12. Combine them by carrying the extra tens and ones into the next place.

300 + 180 + 12 = 492

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 200

#7 Identify Subproblems 3.NBT.A.2

Now take 200 away from 492 to get the number that is 200 less.

492 - 200 = 292

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 292 as a count of tens: 292 is 29 groups of ten (with 2 ones left over).

292 = 29 \times 10 + 2

Seeing 292 as 29 tens is just place-value reading.

Answer: 29

4 · Reviewdoes it hold up?

Check: 29 tens = 290, and 292 + 200 = 492, which matches the original number 492, so the work is right.

Another way: Guess and check (Tool 6): a number that is 29 tens is 290; verify 290 + 2 + 200 = 492 matches the description, confirming 29 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 3 hundreds, 18 tens, 12 ones into 492 and re-reading 292 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 492 - 200 = 292 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 5 medium

There is a three-digit number made up of $7$ hundreds, $11$ tens, and $20$ ones. The number that is $250$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 7 hundreds, 11 tens, and 20 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 250 from it and ask how many tens make up that result.

Givens

The number is 7 hundreds, 11 tens, and 20 ones.
A second number is 250 less than this one.

Unknowns

How many tens make up the number that is 250 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 7 hundreds is 700, 11 tens is 110, and 20 ones is 20. Combine them by carrying the extra tens and ones into the next place.

700 + 110 + 20 = 830

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 250

#7 Identify Subproblems 3.NBT.A.2

Now take 250 away from 830 to get the number that is 250 less.

830 - 250 = 580

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 580 as a count of tens: 580 is 58 groups of ten (with 0 ones left over).

580 = 58 \times 10 + 0

Seeing 580 as 58 tens is just place-value reading.

Answer: 58

4 · Reviewdoes it hold up?

Check: 58 tens = 580, and 580 + 250 = 830, which matches the original number 830, so the work is right.

Another way: Guess and check (Tool 6): a number that is 58 tens is 580; verify 580 + 0 + 250 = 830 matches the description, confirming 58 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 7 hundreds, 11 tens, 20 ones into 830 and re-reading 580 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 830 - 250 = 580 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 6 medium

There is a three-digit number made up of $6$ hundreds, $13$ tens, and $24$ ones. The number that is $264$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 6 hundreds, 13 tens, and 24 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 264 from it and ask how many tens make up that result.

Givens

The number is 6 hundreds, 13 tens, and 24 ones.
A second number is 264 less than this one.

Unknowns

How many tens make up the number that is 264 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 6 hundreds is 600, 13 tens is 130, and 24 ones is 24. Combine them by carrying the extra tens and ones into the next place.

600 + 130 + 24 = 754

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 264

#7 Identify Subproblems 3.NBT.A.2

Now take 264 away from 754 to get the number that is 264 less.

754 - 264 = 490

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 490 as a count of tens: 490 is 49 groups of ten (with 0 ones left over).

490 = 49 \times 10 + 0

Seeing 490 as 49 tens is just place-value reading.

Answer: 49

4 · Reviewdoes it hold up?

Check: 49 tens = 490, and 490 + 264 = 754, which matches the original number 754, so the work is right.

Another way: Guess and check (Tool 6): a number that is 49 tens is 490; verify 490 + 0 + 264 = 754 matches the description, confirming 49 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 6 hundreds, 13 tens, 24 ones into 754 and re-reading 490 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 754 - 264 = 490 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 7 medium

There is a three-digit number made up of $5$ hundreds, $16$ tens, and $18$ ones. The number that is $300$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 5 hundreds, 16 tens, and 18 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 300 from it and ask how many tens make up that result.

Givens

The number is 5 hundreds, 16 tens, and 18 ones.
A second number is 300 less than this one.

Unknowns

How many tens make up the number that is 300 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 5 hundreds is 500, 16 tens is 160, and 18 ones is 18. Combine them by carrying the extra tens and ones into the next place.

500 + 160 + 18 = 678

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 300

#7 Identify Subproblems 3.NBT.A.2

Now take 300 away from 678 to get the number that is 300 less.

678 - 300 = 378

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 378 as a count of tens: 378 is 37 groups of ten (with 8 ones left over).

378 = 37 \times 10 + 8

Seeing 378 as 37 tens is just place-value reading.

Answer: 37

4 · Reviewdoes it hold up?

Check: 37 tens = 370, and 378 + 300 = 678, which matches the original number 678, so the work is right.

Another way: Guess and check (Tool 6): a number that is 37 tens is 370; verify 370 + 8 + 300 = 678 matches the description, confirming 37 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 5 hundreds, 16 tens, 18 ones into 678 and re-reading 378 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 678 - 300 = 378 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 8 hard

There is a three-digit number made up of $7$ hundreds, $13$ tens, and $22$ ones. The number that is $350$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 7 hundreds, 13 tens, and 22 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 350 from it and ask how many tens make up that result.

Givens

The number is 7 hundreds, 13 tens, and 22 ones.
A second number is 350 less than this one.

Unknowns

How many tens make up the number that is 350 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 7 hundreds is 700, 13 tens is 130, and 22 ones is 22. Combine them by carrying the extra tens and ones into the next place.

700 + 130 + 22 = 852

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 350

#7 Identify Subproblems 3.NBT.A.2

Now take 350 away from 852 to get the number that is 350 less.

852 - 350 = 502

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 502 as a count of tens: 502 is 50 groups of ten (with 2 ones left over).

502 = 50 \times 10 + 2

Seeing 502 as 50 tens is just place-value reading.

Answer: 50

4 · Reviewdoes it hold up?

Check: 50 tens = 500, and 502 + 350 = 852, which matches the original number 852, so the work is right.

Another way: Guess and check (Tool 6): a number that is 50 tens is 500; verify 500 + 2 + 350 = 852 matches the description, confirming 50 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 7 hundreds, 13 tens, 22 ones into 852 and re-reading 502 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 852 - 350 = 502 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 9 hard

There is a three-digit number made up of $8$ hundreds, $14$ tens, and $30$ ones. The number that is $470$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 8 hundreds, 14 tens, and 30 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 470 from it and ask how many tens make up that result.

Givens

The number is 8 hundreds, 14 tens, and 30 ones.
A second number is 470 less than this one.

Unknowns

How many tens make up the number that is 470 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 8 hundreds is 800, 14 tens is 140, and 30 ones is 30. Combine them by carrying the extra tens and ones into the next place.

800 + 140 + 30 = 970

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 470

#7 Identify Subproblems 3.NBT.A.2

Now take 470 away from 970 to get the number that is 470 less.

970 - 470 = 500

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 500 as a count of tens: 500 is 50 groups of ten (with 0 ones left over).

500 = 50 \times 10 + 0

Seeing 500 as 50 tens is just place-value reading.

Answer: 50

4 · Reviewdoes it hold up?

Check: 50 tens = 500, and 500 + 470 = 970, which matches the original number 970, so the work is right.

Another way: Guess and check (Tool 6): a number that is 50 tens is 500; verify 500 + 0 + 470 = 970 matches the description, confirming 50 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 8 hundreds, 14 tens, 30 ones into 970 and re-reading 500 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 970 - 470 = 500 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Variant 10 hard

There is a three-digit number made up of $9$ hundreds, $10$ tens, and $40$ ones. The number that is $540$ less than this number is made up of how many tens?

Your answer

Show solution

1 · Understandwhat's really being asked

A number is described loosely as 9 hundreds, 10 tens, and 40 ones -- the tens and ones may go past a single digit, so I first regroup to find the real number. Then I subtract 540 from it and ask how many tens make up that result.

Givens

The number is 9 hundreds, 10 tens, and 40 ones.
A second number is 540 less than this one.

Unknowns

How many tens make up the number that is 540 less.

Constraints

10 ones regroup into 1 ten; 10 tens regroup into 1 hundred.
'How many tens' means the total value divided into groups of ten.

2 · Planchoose the strategy

#15 Organize Information in More Ways · also uses: #7 Identify Subproblems

The counts are written in an unusual way, so the key move is to re-organize them into standard place value by carrying. Then the task splits into clear subproblems: find the number, subtract, and re-read the answer as a count of tens.

3 · Execute3 carry out the plan

1Regroup to find the actual number

#15 Organize Information in More Ways 2.NBT.A.1

Add up the values: 9 hundreds is 900, 10 tens is 100, and 40 ones is 40. Combine them by carrying the extra tens and ones into the next place.

900 + 100 + 40 = 1040

Place value lets me trade 10 ones for a ten and 10 tens for a hundred, core Grade 2 understanding of three-digit numbers.

2Subtract 540

#7 Identify Subproblems 3.NBT.A.2

Now take 540 away from 1040 to get the number that is 540 less.

1040 - 540 = 500

Subtracting two three-digit numbers with regrouping is a Grade 3 fluency skill.

3Count the tens

#15 Organize Information in More Ways 2.NBT.A.1

Read 500 as a count of tens: 500 is 50 groups of ten (with 0 ones left over).

500 = 50 \times 10 + 0

Seeing 500 as 50 tens is just place-value reading.

Answer: 50

4 · Reviewdoes it hold up?

Check: 50 tens = 500, and 500 + 540 = 1040, which matches the original number 1040, so the work is right.

Another way: Guess and check (Tool 6): a number that is 50 tens is 500; verify 500 + 0 + 540 = 1040 matches the description, confirming 50 tens.

Standardsmin grade 3

2.NBT.A.1 Understand that the three digits of a three-digit number represent hundreds, tens, and ones — Regrouping 9 hundreds, 10 tens, 40 ones into 1040 and re-reading 500 as tens.
3.NBT.A.2 Fluently add and subtract within 1000 — Computing 1040 - 540 = 500 with regrouping.

💡Takeaway. Trade your tens and ones into neat place value, then reading the result as a count of tens is easy Grade 3 sense!

Ten in a place carries forward · 10 practice problems

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