Posted by Sam on Sunday, October 14, 2012 at 3:57pm.
The doubling time of a city's population is 17 years. How long does it take for the population to quadruple?

Math  Steve, Sunday, October 14, 2012 at 4:02pm
as long as it takes to double twice: 34 years

Math  Sam, Sunday, October 14, 2012 at 4:03pm
How did you get that?

Math  Steve, Sunday, October 14, 2012 at 4:07pm
come on, man. quadrupling means doubling twice. Each doubling takes 17 years.
after 17 years, the initial population P has grown to 2P
after 17 more years, the population 2P has grown to 2(2P) = 4P, and is quadruple the initial population of P.