Question

Related rates problems:

Answer 1

A pebble is dropped into a calm pond, causing ripples in the form of concentric circles. The radius \(\large r\) of the outer circle is increasing at \(\large 1 ft/sec\) When the radius equals \(\LARGE 4ft\), at what rate is the total area of the disturbed water changing?

Answer 2

rate of change of radius
=dr/dt=1ft/sec

Answer 3

now area of circle=A=pi*r^2
rate of change of area=dA/dt=pi*2*r*dr/dt
at r=4feet
dA/dt=pi*2*4*1.........as dr/dt=1
dA/dt=8*pi

Answer 4

=rate of change of area at r=4

Answer 5

@Luigi0210

Answer 6

Hmm, makes sense, thanks :)

Answer 7

u got it right ??

Answer 8

im to stupid for this D: thanks for helping me to

Answer 9

Yea I got it :)