6.7 Percent Equations

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?
1 st : What are we looking for? Percent, Part, or Whole?
2 nd : 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?
1 st : Percent, Part or Whole? 2 nd : Write an Equation. 3 rd : 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!

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6.7 Percent Equations

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6.7 Percent Equations — Presentation Transcript