SOLUTION: I'm having trouble setting up the equation or even identifying the geometric formula for a couple of word problems. Here they are: 1. The diameter of a metal washer is 4 cm. The

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Question 763466: I'm having trouble setting up the equation or even identifying the geometric formula for a couple of word problems. Here they are:
1. The diameter of a metal washer is 4 cm. The diameter of the hole is 2 cm. How many square centimeters of metal are there in 50 washers? Express the answer in terms of pie.
2. A circular pool is 34 feet in diameter and has a flagstone walk around it that is 3 feet wide. Find the area of the wall. Express the answer in terms of pie.
Answer by Cromlix(4381) (Show Source):
You can put this solution on YOUR website!
1) Radius of washer = 2cm.
Area of washer = Pi*radius^2
= Pi * 2^2
= Pi * 4
= 12.57cm^2
Radius of hole = 1cm
Area of hole = Pi*r^2
= Pi*1^2
= Pi * 1
= 3.14cm^2
12.57cm^2 - 3.14cm^2 = 9.43cm^2 of metal
50 * 9.43cm^2 = 471.5cm^2 of metal.
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2) Radius of pool + walkway = 20 feet
Area of pool + walkway = Pi * r^2
= Pi * 20^2
= Pi * 400
= 1256.64 feet^2
Radius of pool = 17 feet
Area of pool = Pi * r^2
= Pi * 17^2
= Pi * 289
= 907.92 feet^2
Area of (pool + walkway) - pool
1256.64 feet^2 - 907.92 feet^2
= 348.72 feet^2 (the area of the walk.)