Write the heights down, take the cubes off there, then read the views · 12 practice problems
6.G.A.4
0 / 12 solved
Generated variants — 12
Freshly produced from the archetype’s parameters — problem, figure, and solution derived together.
Variant 1easyanswer: Front: columns 1, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
A shape is built from 10 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 10 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 10 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
10−3=7
7 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=1,2,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,1,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 1, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 7, which is the 10 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 2mediumanswer: Front: columns 2, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=2,2,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,1,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 2, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 3easyanswer: Front: columns 2, 1 and 1 high. Side: columns 1, 2 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=2,1,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,2,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 2, 1 and 1 high. Side: columns 1, 2 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 4easyanswer: Front: columns 3, 2 and 0 high. Side: columns 1, 1 and 3 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=3,2,0
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,1,3
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=3
They do.
Answer:Front: columns 3, 2 and 0 high. Side: columns 1, 1 and 3 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 5mediumanswer: Front: columns 2, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=2,2,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,1,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 2, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 6easyanswer: Front: columns 2, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=2,2,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,1,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 2, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 7mediumanswer: Front: columns 2, 2 and 1 high. Side: columns 1, 2 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=2,2,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,2,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 2, 2 and 1 high. Side: columns 1, 2 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 8hardanswer: Front: columns 2, 1 and 1 high. Side: columns 1, 1 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=2,1,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,1,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 2, 1 and 1 high. Side: columns 1, 1 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 9hardanswer: Front: columns 2, 2 and 1 high. Side: columns 0, 2 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=2,2,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=0,2,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 2, 2 and 1 high. Side: columns 0, 2 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 10hardanswer: Front: columns 1, 1 and 2 high. Side: columns 1, 1 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=1,1,2
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,1,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 1, 1 and 2 high. Side: columns 1, 1 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 11mediumanswer: Front: columns 1, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
A shape is built from 11 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 11 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 11 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
11−3=8
8 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=1,2,1
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,1,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 1, 2 and 1 high. Side: columns 1, 1 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 8, which is the 11 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.
Variant 12hardanswer: Front: columns 1, 2 and 2 high. Side: columns 1, 2 and 2 high, front to back.
A shape is built from 12 unit cubes. After the 3 red cubes are taken away, draw what it looks like from the front and from the side.
Did yours match the answer?
Show solution
1 · Understandwhat's really being asked
A stack of 12 cubes loses 3 of them, each from the top of its own stack. We want the front and side views of what is left.
Givens
The stack starts with 12 unit cubes.
3 cubes are removed, each the top of its stack.
Unknowns
The views from the front and from the side afterwards.
Constraints
Only top cubes are removed, so nothing is left floating.
2 · Planchoose the strategy
#15 Organize Information in More Ways · also uses: #17 Visualize Spatial Relationships#2 Make a Systematic List
Redrawing from the picture loses the cubes hidden behind others. Write the heights into a top-view grid instead, do the removal there, and each view is then the largest number along a line.
3 · Execute4 carry out the plan
1Take the cubes off the grid
#15 Organize Information in More Ways6.G.A.4
Each removed cube is the top of its stack, so its cell drops by one.
12−3=9
9 cubes left.
2Read the front view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the front, each column shows only its tallest stack.
front=1,2,2
Left to right.
3Read the side view
#17 Visualize Spatial Relationships6.G.A.4
Looking from the side, each row shows only its tallest stack, front row first.
side=1,2,2
Front to back.
4Check the two agree
#2 Make a Systematic List6.G.A.4
Both views must reach the same tallest stack.
max=2
They do.
Answer:Front: columns 1, 2 and 2 high. Side: columns 1, 2 and 2 high, front to back.
4 · Reviewdoes it hold up?
The heights left add to 9, which is the 12 we started with less the 3 removed.
Another way:Redrawing the solid and looking at it gives the same views, if no cube hidden behind another is forgotten -- which is the part the grid makes safe.
Standardsmin grade 6
6.G.A.4 Surface area using nets of 3D figures — Taking the front and side views of a stack of cubes.
💡Takeaway.Write the heights down before you change anything. Then each view is just the biggest number in its line.