Exercise 4 Page 251

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. We can represent a is p percent of wwith the given proportion. part/whole=percent/100 ⇔ a/w=p/100We can find what 120% of 80 is by thinking about 120 as the percent and 80 as the whole. Let's substitute p= 120 and w= 80 into the formula and solve for a using the Properties of Equality.

a/w=p/100

SubstituteII

p= 120, w= 80

a/80=120/100

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Solve for a

MultEqn

LHS * 80=RHS* 80

a/80* 80=120/100 * 80

FracMultDenomToNumber

a/80* 80 = a

a=120/100 * 80

MoveRightFacToNum

a/c* b = a* b/c

a=120* 80/100

Multiply

Multiply

a=9600/100

CalcQuot

Calculate quotient

a= 96

Knowing the value of a, let's look at the completed percent proportion. 96/80=120/100 We found that 96 is 120 % of 80.

Checking Our Answer

Checking Our Answer

We can use a model to check our answer.