Question -
Answer -
Since the length (x) is decreasing at the rateof 5 cm/minute and the width (y) isincreasing at the rate of 4 cm/minute, we have:
and 
(a) The perimeter (P) of a rectangle is givenby,
P = 2(x + y)
Hence, the perimeter is decreasing at the rate of 2cm/min.
(b) The area (A) ofa rectangle is given by,
A = x⋅ y
When x =8 cm and y =6 cm,
Hence, the area of the rectangle isincreasing at the rate of 2 cm2/min.