So my question is-
A fire has started in a dry open field and is spreading in the form of a circle. If the radius of this circle increases at the rate of 6 feet/ minute express the total area A as a of time t (in minutes).
It seems to me that area would = time(6(pi)time^2)
The answer in the book says the answer is= 36(pi)time^2
It is not clear to me why the 6 must be squared.