# Inflation rate of 9% per year. Use the approximate double time formula to find what the price is in 11 years if the item costs $100 today.?

### 1 Answer

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- 3 weeks ago
100 * 1.09^11 =>

258.04264053054077850709

The doubling time approximation is known as the rule of 70.

11 / (70/9) =>

99/70 =>

100/70, roughly =>

1.42, roughly

100 * (1 + 1.42) =>

100 * 2.42 =>

242

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