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Quantitative Finance · Glossário

O que é Rule of 72?

Definition 8.2 The Interview Book · Capítulo 8 — Mental Arithmetic

The rule of 72 approximates the number of periods an amount takes to double at a rate of rr per cent a period, compounded once a period, by 72/r72/r. The exact doubling time is ln⁡2/ln⁡(1+r/100)\ln 2 / \ln(1 + r/100).

Relative error of three rules for the doubling time against the exact 2/ (1+r), for rates compounded once a period. The rule of 72 crosses zero near 7.85%, the rule of 70 near 2%; the rule of 69.3 is always below. Data: fig_iv_rule72.py.
Figure 8.1. Relative error of three rules for the doubling time against the exact ln⁡2/ln⁡(1+r)\ln 2/\ln(1+r), for rates compounded once a period. The rule of 72 crosses zero near 7.85%, the rule of 70 near 2%; the rule of 69.3 is always below. Data: fig_iv_rule72.py.
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