What is the range of 16.20, 15.50, 14.40, 16.30, 16.20, 15.40, 16.10, 16.10 and 15.30 mins

First we pull out 16.30 since it is the biggest and then take out 14.40 since it is the smallest 

So, we have to subtract the numbers that we took out
   Like: 

16.30   -   14.40 = 1.90  which can also look like this 16.30 - 14.40 = 1.9

Therefore your answer would have to be: 1.90 aka 1.9 

Good Luck! 

45% are boys of the 40 students
45% * 40 is 18

There are 18 boys in the gym

Hope this helps :)