SOLUTION: I need to find the radius. The surface area is 314cm squared and the height is 16cm

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Question 944845: I need to find the radius. The surface area is 314cm squared and the height is 16cm
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
you must have a cylinder
find the radius if the surface area ( of a cylinder)is 314cm%5E2 and the height is h=16cm
Surface_+Area+=+2%28pi%2A+r%5E2%29+%2B+%282pi%2Ar%29%2A+h
314+=+2%28pi%2A+r%5E2%29+%2B+%282pi%2Ar%29%2A+16cm
314=+2%283.14%29%2A+r%5E2+%2B+2%2A3.14%2Ar%2A16
314=6.28%2A+r%5E2+%2B+100.48%2Ar
6.28r%5E2+%2B+100.48r-314=0 ......use quadratic formula

r+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
r+=+%28-100.48+%2B-+sqrt%28+100.48%5E2-4%2A6.28%2A%28-314%29+%29%29%2F%282%2A6.28%29+
r+=+%28-100.48+%2B-+sqrt%28+10096.2304%2B7887.68+%29%29%2F12.56+
r+=+%28-100.48+%2B-+sqrt%28+17983.9104%29%29%2F12.56+
r+=+%28-100.48+%2B-+134.1041028455133%29%2F12.56+
solutions:
r+=+%28-100.48+%2B+134.1041028455133%29%2F12.56+
r+=+33.62410284551327%2F12.56+
r++=+2.67708+
or
r+=+%28-100.48+-+134.1041028455133%29%2F12.56+
r+=+-234.5841028455133%2F12.56+
r+=+-18.6771 => we need only positive value r+=++2.67708cm+

so, your answer is: highlight%28r+=++2.67708cm%29+