# 7. The length x of a rectangle is decreasing at the rate of 5 cm/minute and the width y is increasing at the rate of 4 cm/minute. When x = 8cm and y = 6cm, find  the rate of change of (a) the perimeter of rectangle

Given =   Length x of a rectangle is decreasing at the rate   =   -5  cm/minute                  (-ve sign indicates decrease in rate)
the width y is increasing at the rate    = 4 cm/minute
To find =      and      at  x = 8 cm and y = 6 cm                     , where P is perimeter
Solution:-

Perimeter of rectangle(P) = 2(x+y)

Hence, Perimeter decreases at the rate of

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