Question

A rectangle is twice as long as it is broad. Find the rate of change of the perimeter when
the breadth of the rectangle is 1m and its area is changing at the rate of 18cm2
/s.

Answer 1

length=2*width
area=length*width= width*2width=2 width^2
width= sqrt (area/2)
Perimeter= 2 width + 2 length= 2width+4width=6*width
perimeter=6 sqrt(area/2)
dP/dt=6 d(sqrt(area/2))/dt
take the derivative, and you have it.

Answer 2

thanks

Answer 3

A rectangle is twice as long as it is broad. Find the rate of change of the perimeter when the breadth of the rectangle is 1m and its area is changing at the rate of 18cm2 /s.