5 ms·
10 calculations to know
- eru 18y agoDo not use #10 of the computations. Those are evil approximations exploiting the fact that hyperbolas can look like the logarithm.
- cperciva 18y agoIt's an evil approximation, but it's a very good approximation. For 2% interest, the "rule of 72" tells you that it takes 72/2 = 36 years for money to double; in fact, it takes 70/2 = 35 years. For 5% interest, the "rule of 72" says that it takes 72/5 = 14.4 years; in fact, it takes 71/5 = 14.2 years. For 8% interest, the "rule of 72" says that it takes 72/8 = 9 years, and is correct. For 11% interest, the "rule of 72" says that it takes 72/11 = 6 + 6/11 years; in fact, it takes 73/11 = 6 + 7/11 years. For 14% interest, it takes 74/14 years instead of 73/14 years. Even when you get up to 20% interest, the approximation is close -- it predicts 3.6 years, where the correct value is 3.8 years.
- eru 18y agoI just like the word evil. No moral judgement implied.