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Glencoe Math: Course 1, Volume 1

GM

Glencoe Math: Course 1, Volume 1 View details

8. Solve Percent Problems

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Exercise 3 Page 158

The percent proportion is a proportion that equates a part of a whole to a percent out of 100.

400

Practice makes perfect

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 ⇔ a/b=p/100We can find what number 120 is 30 percent of by thinking about 120 as the part of a whole number b. Let's substitute a= 120 and p= 30 into the formula and solve for b using the Properties of Equality.

a/b=p/100

a= 120, p= 30

120/b=30/100

▼

Solve for b

LHS * 100=RHS* 100

120/b* 100=30/100 * 100

FracMultDenomToNumber

a/100* 100 = a

120/b* 100=30

MoveRightFacToNum

a/c* b = a* b/c

12 000/b=30

LHS * b=RHS* b

12 000/b* b=30 * b

FracMultDenomToNumber

a/b* b = a

12 000=30 * b

a/b=.a /30./.b /30.

12 000/30=b

Calculate quotient

400=b

Rearrange equation

b= 400

Knowing the value of b, let's look at the completed percent proportion. 120/400=30/100 Therefore, 120 is 30 % of 400.

Subchapter links

Guided Practice p.158

Independent Practice p.159-160

H.O.T. Problems p.160

Standardized Test Practice p.160-162

Extra Practice p.161

Common Core Review p.162