Question

the ratio of radii of two circles is 1:3 find the ratio of their areas

Answer 1

Let the radii of circles be a and 3a

Area of 1st circle = pi a^2

A1 = pi a^2 ------(1)

Area of 2nd circle = pi *(3a)^2

A2 = 9 pi a^2 ------(2).

A1 : A2 = (pi a^2) / 9 (pi a^2)

= 1/9

= 1:9

Answer 2

let radii be x&3x
ratio of area. πx^2/π9x^2
1:9 is ratio
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