Question

Two similar circles are shown. The circumference of the larger circle, with radius OB, is 3 times the circumference of the smaller circle, with radius OA.

Two circles are shown. The smaller circle has radius O A and the larger circle has radius O B.

Radius OB measures x units. Which expression represents the circumference of the smaller circle with radius OA?

(StartFraction pi Over 3 EndFraction)x units
(StartFraction 2 pi Over 3 EndFraction)x units
2πx units
6πx units

Answer 1

(StartFraction 2 pi Over 3 EndFraction)x units

Explanation:

edg 2021

Answer 2

The circumference of the smaller circle is:

C = 2*pi*x/3

Explanation:

We know that for a circle of radius R the circumference is given by:

C = 2*pi*R

where pi = 3.14...

Here we have two circles, A and B, where B is the larger circle and A is the smaller circle.

We know that:

The circumference of B is 3 times the circumference of A.

The radius of circle B is: OB = x

The radius of circle A is: OA

We want to find an expression of OA.

The circumference of circle B will be:

C(B) = 2*pi*OB = 2*pi*x

The circumference of circle A will be:

C(A) = 2*pi*OA

And we know that the circumference of circle B is 3 times the circumference of circle A, then:

C(B) = 3*C(A)

replacing the equations for the circumferences, we get:

2*pi*x = 3*(2*pi*OA)

dividing both sides by 2*pi, we get:

x = 3*OA

Now we want to solve this for OA, then we need to isolate it,

x/3 = OA

We can conclude that the radius of the smaller circle is equal to x/3.

Then the circumference of circle A is:

C(A) = 2*pi*x/3