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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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