Question

The ratio of the diameter of two circles is 2:5 what is the ratio of the areas of the circles

Answer 1

`A=\pi r^2= (\pi d^2)/(4)`
(at diameter = 2):
`(\pi*2^2)/(4) = \pi`
(at diameter = 5):
`(\pi * 5^2)/(4) = (25)/(4) \pi`

ratio =
`\pi`:
`(25)/(4) \pi` =
`1: (25)/(4)` =
`4:25`