Ratios:

A ratio is the comparison of two values, usually a part and a whole. 

Example: 3 to 15 can be expressed as 3:15 or 3/15

Remember a ratio is just a division problem nothing more.

Problem:

Lucy made 9 out of 15 basketball free-throw shots. Ann made 18 of 25 basketball free-throw shots. What is the difference between Lucy's free-throw percentage and Ann's free-throw percentage?

a) 9%
b) 12%
c) 18%
d) 25%
e) 60%

Solution: Notice that you must compare the percentages not the actual free-throws. So the goal is to write the comparisons as ratios and then change the ratios into percents. 

1.  9 out of 15 is 9/15

2.  9/15 is 60%  (9 divided by 15)

3.  18 out of 15 is 18/25

4.  18/25 is 72% (18 divided by 25)

5.  Difference means subtract.

72% - 60% = 12%

VOILIA!! WE HAVE THE ANSWER!!