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Shanina R.

asked • 03/10/16

Finding the Actual Doubling Time (Logarithms and Exponential Models)

This problem involves the Rule of 70, which gives quick estimates of the doubling time of an exponentially growing quantity. If r% is the annual growth rate of the quantity, then the Rule of 70 says
Doubling time in years =(aprox) 70/R

Use the Rule of 70 to estimate how long it takes an $8000 investment to double if it grows at the annual rate 2%. Compare with the actual doubling time.

Round your answer for the actual doubling time to three decimal places.

The doubling time estimated with the rule of is: I got this one, 35.

The actual doubling time is Entry field with incorrect answer years.
I'm not sure how to go about this.

1 Expert Answer


Alan G. answered • 03/10/16

5 (4)

Successful at helping students improve in math!

Shanina R.

Thank you so much for your well answered post, and explanations. I was in the library stressing and tried this as a last resort, and I'm so lucky I got you Alan. You helped a young college freshman understand an important problem for her homework, thank you.


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