2.   A ratio is a way to compare two quantities that are measured in the same units by using division  45 : 100 Ratio

3.   A proportion is an equation that states that two ratios are equal.  45 /100 = 90 / 200 Proportion

4.   To solve a proportion you must:  First cross-multiply  45/ 100 = x / 200 Solving Proportions

5.   Multiply the denominator of the first by the numerator of the second  45 / 100 = x / 200

6.   Then multiply the numerator of the first by the denominator of the second  45 / 100 = x / 200

7.   Make them equal:  45(200) = 100(x)

8.   Solve.  100x = 9000

9.   Since x is being multiplied by 100,  to solve we must now divide by 100 to get x by itself

10.   What you do to one side of the equal sign, you must do to the other side of the equal sign

11.   100x / 100 = 9000 / 100

12.   X = 90 Our Proportion is solved