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

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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) About Me  (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 pi=3.14.
The surface area of the whole outer circle (in square feet) is
pi%2A8%5E2 and half of that is pi%2A8%5E2%2F2
The surface area of the whole inner circle (in square feet) is
pi%2A6%5E2 and half of that is pi%2A6%5E2%2F2
The area we want to calculate (in square feet) is
pi%2A8%5E2%2F2-pi%2A6%5E2%2F2 or %28pi%2A8%5E2-pi%2A6%5E2%29%2F2
%28pi%2A8%5E2-pi%2A6%5E2%29%2F2=%2864pi-36pi%29%2F2=28pi%2F2=highlight%2814pi%29
14%2A3.14=highlight%2843.96%29 which is accurate enough.
Using pi=3.1416 we get
we get
14pi=about43.9823