Chapter 6, Section 7:Percents and Equations

December 15, 2008

Warm-Up• Is OVER Of.

• What percent OF 35 IS 5?

• X/100 = %

• X/100 = 5/35

• 5/35 Is = 5 OVER Of = 35

• 35X = 5(100)

• 35X = 500

• X = 14.2%

Warm Up From Quiz• Three way to write a ratio: a:b, a/b, a to b.• A PROPORTION is an equality of two ratio.• Two figures are SIMILAR if they have

corresponding angles and corresponding sides. • PROBABILITY compares favorable outcomes to

total possible outcomes.• “Odds in favor” describes the relation between

favorable outcomes to unfavorable outcomes. Where as, “odds against” describes the relation between unfavorable to favorable outcomes.

• A number over 100 (#/100) is another way of writing A PERCENT.

Writing and Solving Percent Equations

• Solve a Percent problem by writing and solving an equation.

• When you use a percent in an equation, write it as a decimal.

Finding The Percent

• What Percent Of 40 is 6?

• N • 40 = 6

• N = 6/40

• N = 0.15

• N = 15%

Equation

The unknown is the percent TIMES the whole.

6 is the percentage of the whole.

Finding the Part

• What is 15% of 40?

• N = 0.15 • 40

• N = 0.15 • 40

• N = 6

• 6 is 15% of 40

Equation

The unknown is 15% of 40. 6 is the PART of 40

40 is the whole.

Finding the Whole• 6 is 15% of what?

• 6 = .15 • N

• 6/.15 = N

• 40 = N

• 6 is 15% of 40

Equation

The unknown is the whole here.

6 is 15% of a whole that we don’t know.

What is 85% of 62?

• 1st: What are we looking for? Percent, Part, or Whole?

• 2nd: Looking for Part: Write an equation, with the Percent as a Decimal.

• N = .85 • 62

• Simplify: N = 52.7

• 85% of 62 is 52.7 (52.7 = Part of 62)

This Works For Percentages Greater Than 100 As All.

• What percent of 48 is 54?

• What are we looking for?

• Write an Equation.

• N • 48 = 54

• Simplify: N = 54/48 = 1.125

• Move the Decimal point 2 times.

• N = 112.5%

Write an Equation and Solve It

• What is 45.5% of 20?

• 380 is 125% of what number?

N = 0.455 • 20, N = 9.1

380 = 1.25 • N, N = 304

Using Equations to Solve Percent Problems

• Commission: The amount of money a job pays you based on how much you sell.

• REAL LIFE FOLKS!

• A real estate agent makes a 4.5% commission on property she sells. How much does she make on the sale of a house for $245,000?

Real Estate Game of Life• A real estate agent makes a 4.5% commission on

property she sells. How much does she make on the sale of a house for $245,000?

1st: Percent, Part or Whole?

2nd: Write an Equation.

3rd: Simplify and Solve.

Amount of Commission

IS 4.5% OF $245,000

C

Commission

= .045 X $245,000

Commission, C = $11,025.00

Elvis Lives!

• If Elvis was alive when CDs were invented he would receives 5% of royalty on each CD sale. To the nearest cent, find Elvis’s royalty for each CD that sells for $16.99.

The singer makes $0.85 off of each CD sale.

Peanut Butter

• In a survey, 922 people, or about 68.6%, preferred smooth peanut butter to chunky. How many people were surveyed?

1,344 people were surveyed.

Assignment #48

• Page 312-313: 7-20 all. 31-36 all.

• Make sure you complete ALL parts of each problem!