SOLUTION: I have a math problem where pi=22/7 and i have to find the area of a circle using pi with a diameter of 3 1/2. So I know the formula A=pi times r squared. but i cant figure out t

Algebra ->  Surface-area -> SOLUTION: I have a math problem where pi=22/7 and i have to find the area of a circle using pi with a diameter of 3 1/2. So I know the formula A=pi times r squared. but i cant figure out t      Log On


   

Question 314568: I have a math problem where pi=22/7 and i have to find the area of a circle using pi with a diameter of 3 1/2.
So I know the formula A=pi times r squared.
but i cant figure out the correct answer to this problem. Can you explain?
Found 2 solutions by Fombitz, nerdybill:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Change 3 1/2 to a fraction.
D=3%2B1%2F2=6%2F2%2B1%2F2=7%2F2
The radius is (1/2) of the diameter.
R=%281%2F2%29D=%281%2F2%29%287%2F2%29=7%2F4
Then the area,
A=pi%2AR%5E2=%2822%2F7%29%287%2F4%29%5E2
A=%2822%2F7%29%2849%2F16%29
A=%2822%2A7%29%2F16=%2811%2A7%29%2F8
highlight%28A=77%2F8%29 or if you want to get back to a mixed number,
77%2F8=9%2B5%2F8

Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
I have a math problem where pi=22/7 and i have to find the area of a circle using pi with a diameter of 3 1/2
.
+A+=+%28pi%29r%5E2+
Of course, radius(r) is simply half the diameter so
r = (1/2)(3.5) = 1.75 or 1 3/4 or 7/4
.
Plug the given info into:
+A+=+%28pi%29r%5E2+
+A+=+%2822%2F7%29%287%2F4%29%5E2+
+A+=+%2822%2F7%29%2849%2F16%29+
+A+=+%2822%29%287%2F16%29+
+A+=+%2811%29%287%2F8%29+
+A+=+77%2F8+ square units