Application of DerivativeHard
Question
A stone is dropped into a quiet lake and waves move in a circle at a speed of 3.5 cm/sec. At the instant when the radius of the circular wave is 7.5 cm. The enclosed area increases as fastly as-
Options
A.52.5 πcm2/sec
B.50.5 πcm2/sec
C.57.5 πcm2/sec
D.62.5 πcm2/sec
Solution
V = 3.5 cm/sec = 
r = 7 . 5 ; A = πr2
= 2πr × 
= 2 × π × 7.5 × 3.5 = 7 × 7.5 × π
= 52.5 π cm2/sec
r = 7 . 5 ; A = πr2
= 2πr × = 2 × π × 7.5 × 3.5 = 7 × 7.5 × π= 52.5 π cm2/secCreate a free account to view solution
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