The length of a rectangle is increasing at a rate of 9 cm/s and its width is increasing at a rate of 3 cm/s. When the length is 7 cm and the width is 4 cm, how fast is the area of the rectangle increasing?

Given :

The length of a rectangle is increasing at a rate of 9 cm/s and its width is increasing at a rate of 3 cm/s.

When the length is 7 cm and the width is 4 cm .

To find :-

how fast is the area of the rectangle increasing?

Solution :-

As we know that :-

A = lb

To find the rate :-

d(A)/dt = d(lb)/dt .

Differenciate :-

dA/dt = l (db/dt ) + b (dl/dt )

Substitute :-

dA/dt = 9*4 + 7*3

dA/dt = 36 + 21 cm²/s

dA/dt = 57 cm²/s

$450

step-by-step explanation:

first, you have to multiply 150x2=300

next, you have to add 150+300= 450

answer is the third choice:

3x^5+4x^4+x^3+2x^2-10x-7=0

step-by-step explanation: