# Math

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the formula for the surface area of a cylinder is: A=2πrh+2πr^2 If the height of the cylinder is 10 inches, and the surface area is 200 sq. inches, determine the length of the radius

• Math -

A = 2 ð r h + 2 ð r ^ 2

2 ð r 10 + 2 ð r ^ 2 = 200 Divide both sides by 2 ð

10 r + r ^ 2 = 100 / ð

r ^ 2 + 10 r - 100 / ð = 0

100 / ð = 31.831

Y>ou nust solve equation :

r ^ 2 + 10 r - 31.831 = 0

The solutions are :

2.54 in

and - 12.54 in

Radius can't be negative, so soution are:

r = 2.54 in

P.S.

If you don't know how to solve equation

When you see list of results click on:

When page be open in rectangle type:

r ^ 2 + 10 r - 31.831 = 0

and click option: solve it

You will see solution step-by step

• Math -

ð = pi

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