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## anonymous 5 years ago Use the rule of 70 to find the approximate doubling time for a population whose annual growth rate is 0.7% (U.S.)? and 1.2% (World)?

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1. anonymous

i thought it was the rule of 72! it says doubling time is $\frac{72}{r}$

2. anonymous

so first one would be $\frac{10}{.7}=100$

3. anonymous

second would be $\frac{70}{1.2}=58.3$ rounded

4. anonymous

there is rule of 70 I just dont have my book for the formula

5. anonymous

i think 72 is closer, but it is just an approximation in any case

6. anonymous

fine use 70. close enough. it is rule of thumb, not an exact answer.

7. anonymous

thanks

8. anonymous

welcome!

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