SOLUTION: find the area of a circular ring formed by the circumference of two concentric circles of raddii 11m and 4 m. also find the cast of painting this ring at the rate of Rs. 21 per m s

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Question 1070878: find the area of a circular ring formed by the circumference of two concentric circles of raddii 11m and 4 m. also find the cast of painting this ring at the rate of Rs. 21 per m sq.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
The area is,
A=pi%2A%28R%5B2%5D%5E2-R%5B1%5D%5E2%29
A=pi%2A%2811%5E2-4%5E2%29
A=pi%2A%28121-16%29
A=105%2Apim%5E2
The cost would be,
C=105pi%2A21
Work that out for a final answer.