SOLUTION: a 39 ounce can of hills bros. coffee requires 188.5 square inches of aluminum. if its height is 7 inches, what is its radius?

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Question 209457: a 39 ounce can of hills bros. coffee requires 188.5 square inches of aluminum. if its height is 7 inches, what is its radius?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
a 39 ounce can of hills bros. coffee requires 188.5 square inches of aluminum.
if its height is 7 inches, what is its radius?
:
The cylinder surface area formula: S.A. = 2%2Api%2Ar%5E2 + 2%2Api%2Ar%2Ah
S.A. = 188.5; h = 7
2%2Api%2Ar%5E2 + 2%2Api%2Ar%2A7 = 188.5
2%2Api%2Ar%5E2 + 14%2Api%2Ar = 188.5
Divide by 2%2Api
r^2 + 7r = 188.5%2F%282%2Api%29
r^2 + 7r = 30
:
A quadratic equation
r^2 + 7r - 30 = 0
:
Factor this to
(r+10)(r-3) = 0
;
Positive solution
r = 3 inches is the radius
:
:
Check solution
2%2Api%2A3%5E2 + 2%2Api%2A3%2A7 =
56.55 + 131.95 = 188.5