Exercise 19 Page 127

Let's start by recalling that 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 We want to find the number of which 45 % is 9, which means that we want to find the whole. Let w represent the whole. 9/w=45/100 Now we can solve the proportion we got for w. Let's do this by using the fact that the cross products of any proportion are equal.

Finally, we will use the Division Property of Equality to get the value of w.

We got that w= 20 is a solution to the proportion. This means that 9 is 45 % of 20.