SOLUTION: hello there i came across this problem in which i coudnt understand how it got to the answer half circle inner radius is 6 ft the width of outer radius is 2ft find the appr

Question 712322: hello there
i came across this problem in which i coudnt understand how it got to the answer
half circle inner radius is 6 ft the width of outer radius is 2ft
find the approximate area
the answer provided was 43.96 sq ft-
im assuming the formula used was area of a circle= (pi)r^2 then divide by 2
pls help
thanks
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
What you mean is half of the space between two concentric circles,
the inner one with a 6-foot radius,
and the outer one with an 8-foot radius:
The surface area of the space bounded by the two circles (red and blue),
and the (green) line that splits the circles is calculated to about 43.96,
when using .
The surface area of the whole outer circle (in square feet) is
and half of that is
The surface area of the whole inner circle (in square feet) is
and half of that is
The area we want to calculate (in square feet) is
or

which is accurate enough.
Using we get
we get

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