Can I do the Rule of 70 in Reverse?

I am suppose to solve a group of questions using the Rule of 70. I know it is 70/%. but I am not sure how to use it to solve this:

"If Italy took 15 years to double its real GDP capita, what was its average annual GDP per capita growth rate during this period?"
How do I find the percentage? This is the entire question.

EconMakesHeadHurt said:

I am suppose to solve a group of questions using the Rule of 70. I know it is 70/%. but I am not sure how to use it to solve this:

"If Italy took 15 years to double its real GDP capita, what was its average annual GDP per capita growth rate during this period?"
How do I find the percentage? This is the entire question.

Click to expand...

In algebra, it is a GREAT idea to use letters for variables and to define what the variables are. It will prevent tons of confusion.

y = periods (usually years) for some number to double (approximately).

g = average growth rate per period (usually years) as a percentage So 0.05 is written as 5.

Formula is: \(\displaystyle y \approx \dfrac{70}{g}.\)

In your question above, they give you y and ask for g. Can you manipulate the formula algebraically to get the answer requested.

Figured it out myself

70/15

Thank you

Thank you JeffM