SOLUTION: the area of a circle is equal to the area of a rectangle of 12m*6m, find its circumference???

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Question 821251: the area of a circle is equal to the area of a rectangle of 12m*6m, find its circumference???
Answer by LinnW(1048) About Me  (Show Source):
You can put this solution on YOUR website!
C=(pi)(2r)
A=(pi)r^2
Solve for r in the second equation.
A/(pi) = r^2
Take square root of each side.
sqrt( A/(pi) ) = r
Substituting in C=(pi)(2r) we have
C=(pi)(2( sqrt( A/(pi) ) )) or
C=%28pi%29%282%28+sqrt%28+A%2F%28pi%29+%29+%29%29
A in the equation for our problem is l x w = 12*6 = 72
so
C=%28pi%29%282%28+sqrt%28+72%2F%28pi%29+%29+%29%29
= %28pi%29%282%2A6%28+sqrt%28+2%2F%28pi%29+%29+%29%29
= %28pi%29%2812%28+sqrt%28+2%2F%28pi%29+%29+%29%29