SOLUTION: I need help with this one also. An aluminum plate is made according to the following dimensions. The outer radius is 10 in. and the inner radius is 3 in. (a) How many square i

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Question 112342: I need help with this one also.
An aluminum plate is made according to the following dimensions. The outer radius is 10 in. and the inner radius is 3 in. (a) How many square inches in area is the aluminum plate (the outer area)? (b) If the cost to construct the plate is $7.50 per square inch, what is the construction cost?
I appreciate any feedback. Jessie.
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
IF YOU ARE SAYING THAT THERE IS A 3 IN. HOLE IN THE CENTER OF THE PLATE THEN:
AREA=PI*R^2
AREA=3.14*10^2
AREA=3.14*100
AREA=314 IN^2
THE AREA OF THE 3 IN. HOLE:
AREA=PI*3^3
AREA=3.14*9
AREA=28.26 IN^2
SUBTRACTING FOR THE AREA OF THE HOLE WE HAVE LEFT:
314-28.26=285.74 IN^2 IS THE AREA OF THE 10 IN. PLATE WITH A 3 IN. HOLE.
285.74*7.50=$2,143.05 IS THE COST TO CONSTRUCT THIS PLATE.