Question

In 2012 there were approximately 15098000 people aged between 0 and 19 in the UK. Taking the total population to have been around 63183000 at the time, what percentage of the population was aged between 0 and 19?

Answer 1

All you must do is 15098000 divide by 63183000. With that decimal value you receive, the first two is the percentage, the third value, if higher than 4, then round up one percentage. 
Like such: 0.238 rounds to 0.24 which is 24% of the population was aged between 0 and 19.