Problem 28 · 2020 Math Kangaroo
Stretch
Spatial & Visual Reasoning
cube-views
Dirce built the sculpture shown by gluing together cubic boxes that are half a metre on each side. She then painted the whole sculpture except the base it rests on, using a special paint sold in cans. Each can covers 4 square metres. How many cans of paint did she have to buy?
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Answer: B — 4
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Hint 1 of 2
Each cube edge is 0.5 m, so a small face is 0.25 m^2; count painted faces of the stepped solid, skipping the base.
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Hint 2 of 2
Total painted area / 4 m^2 per can, then round up to whole cans.
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Approach: count exposed faces, convert to area, divide by can coverage
- Each cube is 0.5 m on a side, so one face is 0.5x0.5 = 0.25 m^2.
- Count every exposed face of the stepped solid except the bottom support; multiplying by 0.25 gives the painted area.
- Dividing by 4 m^2 per can and rounding up, she needs 4 cans.
Mark:
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