Q. 104.0( 6 Votes )

# 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 π = 22/7.)

Answer :

Let the radius of the circle be r

Area of the circle=

Rate of change of Area

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