Problem 17 · 2022 Math Kangaroo
Stretch
Logic & Word Problems
careful-countingcasework
Wanda chooses some of the shapes shown. She says: “I have chosen exactly 2 grey, 2 big and 2 round shapes.” What is the smallest number of shapes Wanda could have chosen?
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Answer: B — 3
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Hint 1 of 2
You want a shape to count toward more than one of the requirements at once.
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Hint 2 of 2
Pick shapes that are grey-and-big, big-and-round, or grey-and-round to overlap the three needs.
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Approach: make each shape cover two requirements
- She needs exactly 2 grey, 2 big and 2 round.
- Choose a big grey shape (grey+big), a big round shape (big+round) and a small grey round shape (grey+round).
- These three give exactly 2 grey, 2 big and 2 round.
- So the minimum is 3 shapes.
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