25 billion iPhone's sold in 2012 this was 2.2% of all cell phones sold how many cell phones were sold

Question

I know that I need to know how many were sold all together but cannot remember how to figure it out.

Answer 1

We ask what fraction of 100% is 2.2%. To find out we work out: 100/2.2=500/11=45.4545 approx.

Since 100% is 45.4545 bigger than 2.2% we can work out 25 billion times 45.4545 to give us the much larger  number of phones: 25 billion * 45.4545=12500/11 billion = 1136 billion phones (approx).