Problem 15 · 2016 Math Kangaroo
Medium
Spatial & Visual Reasoning
reflectionclock-calendar
Bart sits at the hairdresser's. In the mirror he sees a clock as shown in the diagram. What was the mirror image of the clock 10 minutes earlier?
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Answer: E — Clock E.
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Hint 1 of 3
The picture is already a mirror image, so first flip it left-right to read the real time.
Still stuck? Show hint 2 →
Hint 2 of 3
Move the hands back 10 minutes on that real clock.
Still stuck? Show hint 3 →
Hint 3 of 3
Finally mirror that earlier clock again, because the question asks for the mirror image.
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Approach: undo the mirror, rewind 10 minutes, mirror again
- Flip the mirrored picture left-right to get the true time on the wall.
- Turn the hands back 10 minutes to find the real clock from 10 minutes earlier.
- Now mirror that earlier clock left-right, since Bart only ever sees the mirror image; this matches picture E, choice (E).
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