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A stone is dropped into a quiet lake and...

A stone is dropped into a quiet lake and waves move in circles at a speed of 3.5 cm per second. At the instant when the radius of the circular wave is 7.5 cm, how fast is the enclosed area increasing ? (Take `pi = 22//7`)

A

32.5 `pi cm^(2)//sec`

B

31.5 `pi cm^(2)//sec`

C

52.5 `pi cm^(2)//sec`

D

None of these

Text Solution

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The correct Answer is:
C
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DISHA PUBLICATION-APPLICATION OF DERIVATIVES -EXERCISE - 1
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