Problem 8 · 2018 Math Kangaroo
Medium
Spatial & Visual Reasoning
spatial-reasoning
Lisa needs exactly 3 pieces to complete her jigsaw. Which of the 4 pieces is left over?
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Answer: A — A
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Hint 1 of 3
Look at the empty hole: where does it have bumps sticking in, and where does it have gaps?
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Hint 2 of 3
A bump on a piece must meet a gap, and a gap must meet a bump — they have to fit like puzzle pieces.
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Hint 3 of 3
Three of the pieces fit the hole together; find the one shape that just won't go in.
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Approach: fit pieces into the hole and find the odd one out
- The empty hole is a long rectangle with bumps and gaps along its edges.
- Try each piece in the hole — its bumps must meet the hole's gaps, and its gaps must meet the hole's bumps.
- Three pieces fill the hole exactly, but piece A (with bumps sticking out on every side) cannot fit, so it is left over.
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