Question

The ratio of the radii of two circles is 3:7.
Calculate ratio of their circumferences.
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Answer 1

Step-by-step explanation:

The ratio of the radii of two circles is 3:7.

Calculate ratio of their circumferences.

Answer 2

Step-by-step explanation:

Let, the radii of each cirlcle be 3x and 7x respectively,

We know, the formula for calculating the area for circle is πr^2.

Therefore, the ratio of the circles, are—

π(3)^2 : π(7)^2

= (3)^2 : (7)^2

= 9:49

A very easy method for determining the answers of questions of this same type is just squaring the ratio of the radii, that would represent the ratio of the area and saves a lot of writing, however, this cannot be used in subjective answers. One can only use this for short questions, that too in his mind, not on exam sheets.

E.g. [3:7]^2

= 9:49,