Advanced Math practice question

Answer: 15

Set 400 · 2^(t/5) = 3,200, so 2^(t/5) = 8 = 2³. Then t/5 = 3 and t = 15. (The population doubles every 5 years: 400 → 800 → 1,600 → 3,200 takes three doublings.)

Common wrong answers

If you answered 3

3 is the number of doublings, t/5. Each doubling takes 5 years, so t = 15.

If you answered 8

8 is 3,200 / 400, the growth factor needed — that's 2³, so three doublings, 15 years.

If you answered 40

40 is 8 × 5, confusing the factor 8 with the number of doublings (3).

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