IQR = 6
First locate the median 
at the centre of the data arranged in ascending order. Then locate the lower and upper quartiles 
and 
located at the centre of the data to the left and right of the median.
Note that if any of the above are not whole values then they are the average of the values either side of the centre.
rearrange data in ascending order
15 16 ↓17 17 18 21 22 ↓23 25
↑
= 18
= 
= 16.5
= 
= 22.5
IQR = - = 22.5 - 16.5 = 6
15 /6÷ 5/6
when we divide fractions we do the reciprocal of the second number that is of
5/6 = 6/5 and then multiply it by the first number
15/6 x 6/5
ans) 3
There are 55 multiples of 5 between 81 and 358
I would assume so since it is a repeating decimal.
