How do I find the ratio of the area of circle I and circlle ll ?

The radius of a circle I is one half the radius of circle ll. What is the ratio of the area of circle l to the area of circle ll?

Let’s say circle I has radius of 1 and circle II has a radius of 2. Find the areas:
circle I = π * 1² = π * 1 = π
circle II = π * 2² = π * 4 = 4π

find the ratio between the areas
π / 4π

1/4 or 1:4

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2 Responses to “How do I find the ratio of the area of circle I and circlle ll ?”

Geezah on February 27th, 2010 at 3:01 am

You know that the area of a circle is A = pi * r^2. Let’s say the radius of the smaller circle is "x". Then the radius of the larger circle is "2x". So the ratio of the smaller circle’s area to the bigger circle’s area is pi r^2 : pi (2x)^2, which you can reduce from there. You should get 1:4.
References :
Caiso on February 27th, 2010 at 3:49 am

Let’s say circle I has radius of 1 and circle II has a radius of 2. Find the areas:
circle I = π * 1² = π * 1 = π
circle II = π * 2² = π * 4 = 4π

find the ratio between the areas
π / 4π

1/4 or 1:4
References :

Area List