A quantity grows as , with in years. After how many years does it first double?
Answer and explanation
Correct answer: B.
- Step 1: Doubling means , so .
- Step 2: Take natural logs: .
- Step 3: .
Answer
.
Why not the others: : multiplies by the rate instead of dividing by it. : divides by instead of by . : finds the time to quadruple.
Practise more Exponentials and logarithms.
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