Problem 22 · 2022 Math Kangaroo
Stretch
Fractions, Decimals & Percents
area-fractionpercent-multiplier
A figure is made of a triangle and a circle that partly overlap. The grey area is 45% of the whole figure, and the white part of the triangle is 40% of the whole figure. What percent of the circle’s area is the white part lying outside the triangle?
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Answer: B — 25%
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Hint 1 of 2
Split the shape into three pieces: the white triangle part, the grey overlap, and the white circle part outside.
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Hint 2 of 2
The whole shape is 100%; use 45% grey and 40% white-triangle to find the leftover circle piece, then compare it to the whole circle.
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Approach: track the percent pieces of the figure
- The whole figure is 100%: white triangle 40% plus grey 45% leaves 15% for the white circle part outside the triangle.
- The grey region is the overlap inside the circle, so the whole circle is grey (45%) plus its outside white part (15%) = 60% of the figure.
- The white outside part is 15/60 = 25% of the circle, so the answer is B.
Mark:
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