Exercise 3 Page 158

The percent proportion is a proportion that sets the ratio of a part of a whole equal to the ratio of a percent out of 100. part/whole=percent/100 ⇔ a/b=p/100 We can find what number 120 is 30 percent of by thinking about 120 as the part of a whole number b. Let's substitute a= 120 and p= 30 into the formula and solve for b using the Properties of Equality.

Now that we know the value of b, let's look at the completed percent proportion. 120/400=30/100 Therefore, 120 is 30 % of 400.