Question

A pebble drops in a lake and makes concentric circles in the water. The radius increases at a rate of 5 ft/sec, so r(t)=5t. Formulate a function to represent the area of the outer circle after t seconds. (A = r²)

Answer 1

`25\pi t^2`

Explanation:

After
`t` seconds, the radius is
`5t`.

So, the area is
`\pi(5t)^2=25\pi t^2`.