Hi Laura. Percentages are just fractions where the denominator is 100.

So if you have 20 students and 8 of them are girls, then that means 12 are boys. So boys are 12/20 of the students.

To find the percentage, you convert this to a fraction where the denominator is 100. There are two easy ways to do this:

1. you have to multiply the denominator (20) by 5 to get to 100, so you multiply the numerator by 5 as well: 5 x 12 = 60. So the answer is 60%.
   
   
2. you can just multiply the numerator by 100 and then divide by the denominator. 12 x 100 = 1200. 1200 / 20 = 60. So the answer is 60%.

Use whichever method you find easiest, but the second one is more versatile if you can't immediately see what to multiply the denominator by to get 100.

Cheers,
Stephen La Rocque.