A grey squirrel population was introduced in a certain county of Great Britain 35 years ago. Biologists observe that the population doubles every 7 years, and now the population is 60,000.

(a) What was the initial size of the squirrel population?

If this occurred over a span of 35 years and the population doubles every 7 years, we can divide 35 by 7 to find how many times the population has doubled, which would be 5 times. If we divide 60,000 by 2 (or multiply by 1/2) 5 times, you would get the answer, which would be 1,875.