# The length x of a rectangle in decreasing at the rate of 5 cm/min and the width y increasing at the rate of 4 cm/min,

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The length x of a rectangle in decreasing at the rate of 5 cm/min and the width y increasing at the rate of 4 cm/min, find the rate of change its area when x = 5 cm and y = 8 cm.

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Let A denote the area of rectangle at instant t

(-) ve sign shows that area is decreasing at the rate of 20cm2/min.