You guys did a good job on the last one, so here's a new one:
The length of a rectangle is increasing at a rate of 8 cm/s and its width is increasing at a rate of 3cm/s. When the length is 20 cm and the width is 10 cm, how fast is the area of the rectangle increasing.
2007-11-23 09:27:11 · 3 answers · asked by glass_commander 2 in Science & Mathematics ➔ Mathematics
dx/dt = 8cm/s......dy/dt = 3cm/s
Find da/dt when x = 20 ......... y=10
da/dt = (dx/dt)y + x(dy/dt) = 10x8 + 20 x3 = 140 cm²/ s
2007-11-23 09:36:19 · answer #1 · answered by iceman 7 · 1⤊ 0⤋
For a rectangle, the area A(W,L) is a function of width (W) and length (L).
A(W, L) = WL
Differentiate w.r.t. time t,
A' = W'L + WL' = 3*20 + 10*8 = 140 cm^2/sec
2007-11-23 17:31:52 · answer #2 · answered by sahsjing 7 · 1⤊ 0⤋
8*3=24cm^2/s^2
now need the time to c the rate
2007-11-23 17:32:41 · answer #3 · answered by tinhnghichtlmt 3 · 0⤊ 1⤋