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Question
A circular plate expands uniformly under the influence of heat. If its radius increases from 10.5 cm to 10.75 cm, then find an approximate change in the area and the approximate percentage change in the area
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Solution
Area of the circular plate A = πr2
= π × 10.5 × 105
= 110.25π
dA = 2πrdr
= 2π × 10.5 × 0.251
= 5.25π
Approximate percentage change in the area
= `"dA"/"A" xx 100`
= `(5.25pi)/(110.25pi) xx 100`
= 0.04761 × 100
= 4.76%
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