Question

The ratio of the radii of two circles is 2:5. What is ratio of their circumferences ?

Answer 1

ratio of radii=2:5
so ratio of circumference=?
circumference of circle=2Πr
ratio=
2×Π×2r/2×Π×5r
2:5
so ratio of circumference=2:5

Answer 2

Given :-

The ratio of the radii of two circles is 2:5.

Let first circle's radius be '2x'

and second circle be '5x'

First circle circumference

Circumference =2πr

= 2 × 22/7 × 2x

= 44/7 × 2x

= (88x)/7

Second circle circumference

Circumference = 2πr

= 2 × 22/7 × 5x

= 44/7 × 5x

= (220x)/7

Ratio of two circles circumference =

= $\bf \frac{(\frac{88x}{7})}{(\frac{220x}{7})}$

= $\bf \frac{88x}{7}\times\frac{7}{220x}$

= 2:5

Hence,

so the ratio of the circumference of two circles = 2:5