Question
The area of a variable rectangle is increasing at the rate of 40cm/s. The length of a rectangle is always equal ti the square of the breadth. At what rate the length is increasing at the instant when the breadth is 8cm?
Answers
Steve
a = b*l = b * b^2 = b^3
da/dt = 3b^2 db/dt
40 = 3*64 db/dt
db/dt = 5/24
l = b^2
dl/dt = 2b db/dt = 2*8 * 5/24 = 10/3
da/dt = 3b^2 db/dt
40 = 3*64 db/dt
db/dt = 5/24
l = b^2
dl/dt = 2b db/dt = 2*8 * 5/24 = 10/3