Problem 16 · 2021 Math Kangaroo
Medium
Spatial & Visual Reasoning
sequence-of-figurescareful-counting
Nora plays with 3 cups on the table. In each move she takes the left-hand cup, flips it over, and puts it to the right of the other cups. The picture shows the first move. What do the cups look like after 10 moves?
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Answer: B
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Hint 1 of 2
Draw the up/down pattern after each move and watch for it to come back to the start.
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Hint 2 of 2
Once you know how many moves bring the cups back to the beginning, you can skip ahead to move 10.
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Approach: draw the moves until the pattern repeats, then read off move 10
- Start with all 3 cups upright and flip-and-move the left cup each time: up-up-up turns into up-up-down, then up-down-down, then down-down-down.
- Keep going: down-down-up, down-up-up, and at move 6 the cups are back to up-up-up — so the pattern repeats every 6 moves.
- Move 10 is 4 moves past move 6, so it matches move 4: down-down-up.
- That arrangement is option B.
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