Answer: 8.75 years
Explanation:
To solve this we can use the brilliant rule of 70 which posits in it's simplest form that an amount will double if we decide 70 by it's required rate.
For example if you want to know how long your 20 billion will take to double given a 15% rate you say,
= 70/15
= 4.67 years.
In that same light therefore, we can calculate for this question thus,
= 70/8
= 8.75 years.
If you need any clarification do comment.
