the question is below

Question

The height of a triangle is increasing at 3 cm/min while the area of the triangle is increasing at 4cm2/min. at what rate is the triangle's base changing when the triangle's height is 10 cm and its area is 90cm2?

The rate of change of the base is ______ cm/min.

Answer 1

A = (1/2)bh When A = 90 and h = 10, we have 90 = (1/2)(b)(10). So, b = 18.

dA/dt = (1/2)(db/dt)h + b(dh/dt)

4 = 5(db/dt) + 18(3)

Solve for db/dt.