Question

Question #0b0bf

Answer 1

The annual percentage growth rate of selfies per day over the 2 year period from 2013 to 2015 was `50%`

Explanation:

Information from 2008 is superfluous.
In 2013, there were 200 million selfies taken per day.
In 2015, the average number of selfies/day was 400 million.

The change (annual percentage growth rate of selfies per day) over the 2 year period from 2013 to 2015 is:

`400m-200m=200m` so the number of selfies doubled over the two years.

When a quantity doubles, it has gained `100%` in addition to it's original value.

This occurred over a two year time span. So each year the gain was `(100%)/2=50%`