Problem
Read a mirrored clock, then find elapsed time
Two clocks are shown as seen in a mirror. Read correctly, the 'fell asleep' clock is 4:52 and the 'woke up' clock is 5:37. Find how long Noah napped, in hours and minutes.
Measurement & data
Your answer
Watch out Each clock is a mirror image, so read it flipped back to normal — don't read the reversed face as if it were an ordinary clock.
How to solve
Strategy Visualize Spatial Relationships — First mentally flip each mirrored clock to read the true time, then find the elapsed time between the two real times by adding a jump to the next o'clock plus the leftover minutes.
1STEP 1
Un-mirror both clocks
Flipping the mirror images back to normal reads the true times: fell asleep at 4:52, woke up at 5:37.
asleep 4{:}52, awake 5{:}37
A mirror swaps left and right, so picturing the flip restores the real clock face.
2.MD.C.7Visualize Spatial Relationships2STEP 2
Jump from 4:52 to 5:00
From 4:52 it takes 8 minutes to reach 5:00.
60 - 52 = 8 → 4{:}52 + 8 = 5{:}00
Stepping up to the whole hour first makes the rest of the count easy.
3.MD.A.1Identify Subproblems3STEP 3
Add the minutes to 5:37
From 5:00 to 5:37 is another 37 minutes, so the whole nap is 8 + 37 minutes.
8 + 37 = 45 minutes
Both clocks are in the same span under an hour, so the parts add to under one hour.
3.MD.A.1Identify SubproblemsThe whole nap from 4:52 to 5:37 equals the 8-minute step up to 5:00 plus the minutes from 5:00 to 5:37, added together.
Why?
On the clock the two steps sit end to end — the first ends at 5:00, exactly where the second begins — so together they stretch from 4:52 all the way to 5:37 with nothing skipped and nothing counted twice.
Why?
When pieces cover a whole span with no gap and no overlap, their lengths add back to the length of the whole span.
🧱Whole is the sum of its partsBreak a thing into pieces with no gaps or overlaps and the pieces add back to the whole.
Why?
The first step is 8 minutes long because 52 needs 8 more to reach a full hour of 60 minutes, and that missing amount is exactly what 60 minus 52 gives.
Why?
Taking 52 away from 60 reveals the number that was added to 52 to make 60, because subtracting reverses adding.
🧱Inverse operationsSubtraction undoes addition and division undoes multiplication — they reverse each other.
Answer
45 minutes (0 hours 45 minutes)
Check by adding: 4:52 + 45 minutes = 5:37, which matches the wake-up time. The nap is under an hour, consistent with the times being only 45 minutes apart.
Takeaway
Flip the mirror clock in your head, then count the minutes to the next time: Grade 3 clock-reading plus a spatial flip!
- Un-mirror both clocks
- Jump from 4:52 to 5:00
- Add the minutes to 5:37
Where next?
Another one like thissuggested
Step back and solidifysuggested