SOLUTION: A sphere with a 4 in. radius is being plated with silver for a cost of $30. To the nearest hundredth what is the radius of a sphere which is plated with silver for a cost of $80?

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Question 835462: A sphere with a 4 in. radius is being plated with silver for a cost of $30. To the nearest hundredth what is the radius of a sphere which is plated with silver for a cost of $80?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
The surface area of a sphere is
SA%5Bs%5D=2%2Api%2AR%5E2=2%2Api%2A4%5E2=32%2Api
The cost for that sphere plating is $30.
So the cost per square inch is C=30%2F%2832%2Api%29=15%2F%2816%2Api%29
Now for an $80 job,
80=SA%2A%2815%2F%2816%2Api%29%29
SA=%2880%2A16%2Api%29%2F15
SA=%2816%2A16%2Api%29%2F3
2%2Api%2AR%5E2=%28256%2Api%29%2F3
R%5E2=128%2F3
R=sqrt%28128%2F3%29
Use your calculator to get that to the desired decimal places.