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2018 Math Kangaroo

Problem 11

Problem 11 · 2018 Math Kangaroo Medium
Spatial & Visual Reasoning tiling-tessellationarea

Tom wants to completely cover his paper boat using the two shapes shown (a small square and a trapezoid). What is the smallest number of shapes he needs?

Figure for Math Kangaroo 2018 Problem 11
Show answer
Answer: B — 6
Show hints
Hint 1 of 2
You want to fill the whole boat with no gaps, so try to use the bigger shape as often as it fits.
Still stuck? Show hint 2 →
Hint 2 of 2
Cover the wide bottom of the boat with the big pieces first, then patch the corners with the small ones.
Show solution
Approach: fill the boat using the big piece wherever it fits, then patch the rest, counting pieces
  1. Start by laying the bigger shape across the parts of the boat where it fits exactly.
  2. Fill the leftover corners and edges with the smaller shape so there are no gaps.
  3. The fewest shapes that cover the whole boat is 6, answer B.
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