Question

can anyone help me check my answer for a related rates problem?

Answer 1

I got 1/2 as an answer but when I checked it it was wrong.

Answer 2

well this is how I looked at the problem

for the Area

\[\frac{dA}{dt} = \frac{dA}{dr} \times \frac{dr}{dt}\]

for the circumference

\[\frac{dC}{dt} = \frac{dC}{dr} \times \frac{dr}{dt}\]

you will need to find dA/dr and dC/dr and substitute into the appropriate equations.

then the next part is

\[\frac{dA}{dt} = 2 \times \frac{dC}{dt}\]

substitute and solve for r, it all falls out neatly

Answer 3

or to make it simply

\[\frac{dA}{dr} \times \frac{dr}{dt} = 2 \times \frac{dC}{dr} \times \frac{dr}{dt}\]

Answer 4

@campbell_st so does r=2?

Answer 5

thats what I got...

Answer 6

thank you @campbell_st !