Exercise 27 Page 252

We are told that Franklin was y years old. We also know that 7 is 10% of y. We can find Franklin's age by figuring out what number's 10% is equal to 7. Recall that the percent equation is an equation in which the part is equal to the product of the corresponding percent and the whole. We can represent a is p percent of wwith the following equation. a= p% * wWe can find what number's 10% is equal to 7 by substituting p%= 0.1 and a= 7 into the formula and solve for w using the Properties of Equality.

a= p% * w

SubstituteII

p%= 0.1, a= 7

7= 0.1 * w

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Solve for w

DivEqn

.LHS /0.1.=.RHS /0.1.

7/0.1=0.1* w/0.1

CancelCommonFac

Cancel out common factors

7/0.1=0.1* w/0.1

SimpQuot

Simplify quotient

7/0.1=w

CalcQuot

Calculate quotient

70=w

RearrangeEqn

Rearrange equation

w= 70

Knowing the value of w, let's look at the completed percent equation. 7= 10% * 70 We found that 7 is 10 % of 70. This means that Franklin was 70 years old.

Checking Our Answer

Checking Our Answer

We can use a model to check our answer.