Advanced MathEasy–MediumYears for a colony to reach a size
Advanced Math practice question
A colony of bats has 5 members, and its size after x years is modelled by 5·2ˣ. After how many years will the colony have 40 bats?
Answer: 3
5·2ˣ = 40 gives 2ˣ = 8, so x = 3.
Common wrong answers
- If you answered 4
- 4 gives 5 × 16 = 80.
- If you answered 8
- 8 is 40 ÷ 5, the value of 2ˣ, not x.
- If you answered 35
- 35 subtracts 5 from 40.
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