Wetzel

Math 101

2.4 – Percents, Ratios, & Proportions

What is a percent?

            Complete the table.

            Percent             Decimal            Fraction

               25%                 .25                  

               36%                ______              ______

              _____               .045                  ______

              _____            ______                

What is a ratio?

What is a proportion?

            To Solve:   Cross-Multiply

            1.)  Multiply one numerator by the opposite denominator.

            2.)  Set that equal to the other numerator multiplied by the other denominator.

            3.)  Solve the remaining equation.

Ex.:

1.)                                                                                2.) 

Applications:

I.  Is over Of Method:              

Ex.:

3.)  What percent of 80 is 24?                                                  4.)  What is 600% of 53?

5.)  The average score for a class on test 1 was 88.  The average score for test 2 was 77.  What was the percent decrease in the average score from test 1 to test 2?

II.  Mixture Problems:

            A bartender has rum that is 40% alcohol.  How much rum and how much cola need to be mixed together to make 5 liters of rum and cola that is 16% alcohol?

III.  Interest Problems:  I = Prt

            Diane was given $35,000 when she retired.  She invested some at 7% interest and the rest at 9% interest.  If she earned $2910 in interest in one year, how much was invested in each account?