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.

9/w=45/100

CrossMult

Cross multiply

9* 100= w * 45

Multiply

Multiply

900=45w

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

900=45w

DivEqn

.LHS /45.=.RHS /45.

900/45=45w/45

CancelCommonFac

Cancel out common factors

900/45=45w/45

SimpQuot

Simplify quotient

900/45 = w

CalcQuot

Calculate quotient

20 = w

RearrangeEqn

Rearrange equation

w = 20

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