SOLUTION: A penny has a diameter of 23.05mm and a thinness of 1.45mm. Find the surface area of the conin to the nearest hundredth.

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Question 137510: A penny has a diameter of 23.05mm and a thinness of 1.45mm. Find the surface area of the conin to the nearest hundredth.
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
What are the surfaces on the coin?
You have the front, the back and the rim. The front and back are the same -- just the area of a circle.
The rim (side) can be found using formulas for surface area of cylinders. OR, in this case, you can mentally "unroll" the side. Imagine making a vertical cut and then unrolling. What do you end up with?
Right, you end up a rectangle with sides of 1.45mm and the circumference of the circle making up the front/back.
Net, you have three areas
Surface+area+=+AreaFront+%2B+AreaBack+%2B+AreaSide
A+=+2%2AAreaFront+%2B+AreaSide
The area of a circle is given by A=pi%2Ar%5E2 . we are given the diameter, so we need to divide by 2 to get the radius.
The area of a rectangle is given by A+=+Length%2AWidth. We are given the width and need to calculate the length. The length is just the circumference. Circumference is given by C=pi%2Ad.
Now you have everything you need.
A+=+2%2A%28pi%2A%2823.05%2F2%29%5E2%29++%2B+%28pi%2A23.05+%2A+1.45%29
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