SOLUTION: the diameter of a circular glass frame is 84cm. a 2cm wide metallic border is outside it. find the cost of metal required for bordering the glass frame at Rs.30 per square cm.

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Question 271646: the diameter of a circular glass frame is 84cm. a 2cm wide metallic border is outside it. find the cost of metal required for bordering the glass frame at Rs.30 per square cm.
Answer by mananth(16946) (Show Source):
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the diameter of a circular glass frame is 84cm. a 2cm wide metallic border is outside it. find the cost of metal required for bordering the glass frame at Rs.30 per square cm.
There are two steps to solve this problem
find the area of the glass with 2 cm border
find the area of the glass
Subtract the two to get area of the metal portion
Diameter of glass with border = 86 cm
Area = pi*(d^2/4)
=3.14 *86*86 / 4
5805.86sq. cms.
Diameter of glass is 84 cms
Area of glass is
Area = pi*(d^2/4)
=3.14 *84*84 / 4
= 5538.96
5805.86- 5538.96 = 266.9sq. cms is the area of the metal.
The cost will be 266.9* 30 = Rs. 8007