The area of circle b is 36 times greater than the area of circle

a. if the radius of circle b is 12 feet, what is the radius of circle a?

The formula for area of a circle is pi r^2.

Circle A = pi a^2

Circle B = pi b^2

Now if the area of circle B is 36 times greater than the area of circle A, we can translate than into:

areaB=36*areaA

pi b^2 = 36 pi a^2

pi b^2 = 36 pi 12^2 (sub in variables)

b^2 = 36*12^2 (divide pi from both sides)

b^2 = 36 * 144 (solve 12^2)

b^2 = 5184 (simplify right hand side)

b = 72 (take square root on both sides)

Your answer is 72.

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