The ratio of the radius of two circles is 1: 3, and then the ratio of their areas is_________?
Correct answer: C. 1:9
- A. 1:3
- B. 1:6
- C. 1:9
- D. 1:5
Explanation
Circle area varies as the square of radius. Squaring the radius ratio 1:3 gives areas 1²:3² = 1:9. The likely wrong choice is 1:3, which uses the radius ratio without squaring it.
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Ratios compare quantities in the same units, while proportions state that two ratios are equal. Problems cover simplification, division in a given ratio, direct and inverse variation, scale, and missing terms, with attention to the difference between a ratio and a fraction representing part of a whole.
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