How do I solve this?

Question

Suppose a population of 20 grasshoppers doubles in size every month. How many grasshoppers will

there be after 1 year?

I have solved this before, but it is a review and I have forgotten how to do it..;

Answer 1

Initial population = 20

After Month 1, P1 = 20*2

After Month 2, P2 = (20*2)*2 = 20 * 2²

After Month 3, P3 = (20 * 2²)*2 = 20.2³

..

..

After month n, Pn = 20*2ⁿ

In one year, n =12.

P = 81,920

This is the same answer as another tutor has already provided. But, this is a simple way to never forget how to solve the problem. Hope this helps.

Answer 2

20*2^12=81920...............