Exercise 9 Page 125

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 50 % is 40, which means that we want to find the whole. Let w represent the whole. 40/w=50/100 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.

40/w=50/100

CrossMult

Cross multiply

40* 100= w * 50

Multiply

Multiply

4000=50w

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

4000=50w

DivEqn

.LHS /50.=.RHS /50.

4000/50=50w/50

CancelCommonFac

Cancel out common factors

4000/50=50w/50

SimpQuot

Simplify quotient

4000/50 = w

CalcQuot

Calculate quotient

80 = w

RearrangeEqn

Rearrange equation

w = 80

We got that w= 80 is a solution to the proportion. This means that 40 is 50 % of 80.