Problem 7 · 2009 Math Kangaroo
Easy
Geometry & Measurement
perimeter
The diagram shows squares of different sizes. The side length of the smallest square is 20 cm. How long is the black line?
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Answer: C — 420 cm
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Hint 1 of 2
Read off how the square sizes grow, then add up the straight pieces of the black line.
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Hint 2 of 2
The smallest square is 20 cm; the others are simple multiples, so total the segment lengths.
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Approach: add segment lengths
- Each square's side is a multiple of the smallest 20 cm side.
- The black line is made of straight segments running along the square edges.
- Adding those segment lengths gives 420 cm — answer C.
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