Question

if the ratio of circumference of two circle is 2:3 what is ratio of their radii

Answer 1

2:3 will be the ratio of radius.
Aliter::
2πR:2πr=2:3
=>R:r=2:3

Answer 2

Circumference of circle=2πr
Therefore,
2πr1÷2πr2=2:3
i.e. r1÷r2 =2:3