Lesson 4-3Lesson 4-3Proportions andProportions and

Percent EquationsPercent Equations

Objective: To use proportions Objective: To use proportions when solving percent when solving percent

problems and to write and problems and to write and solve percent problems.solve percent problems.

……and why?and why?

One example of a real world One example of a real world connection is to calculate the connection is to calculate the total water supply of the USA.total water supply of the USA.

PERCENT REMINDERPERCENT REMINDER

A percent is a ratio comparing a number to A percent is a ratio comparing a number to 100.100.

USE THE FOLLOWING PROPORTION FOR USE THE FOLLOWING PROPORTION FOR SOLVING PERCENT PROBLEMS:SOLVING PERCENT PROBLEMS:

‘‘ N* N* ‘‘ = = ‘‘ part part ‘‘

100 whole100 whole

*N/100 is the percent.*N/100 is the percent.

Examples 1 & 2, page 197Examples 1 & 2, page 197

Finding the percent.Finding the percent.

Ex. 1) What percent of Ex. 1) What percent of 40 is 30?40 is 30?

Finding the part.Finding the part.

Ex. 2) Find 30% of 40.Ex. 2) Find 30% of 40.

Example 3, page 198Example 3, page 198

Ex. 3 – Charlie worked 31.5 hours at a hospital as Ex. 3 – Charlie worked 31.5 hours at a hospital as a volunteer. This represents 87.5% of the a volunteer. This represents 87.5% of the school’s requirement for community service. How school’s requirement for community service. How many hours does his school require for many hours does his school require for community service?community service?

Percent EquationsPercent Equations

Key WordsKey Words““What …” is the unknown. What …” is the unknown.

Use Use xx..““Is” means =.Is” means =.““Of” means to multiply.Of” means to multiply.

Ex. 4, page 198Ex. 4, page 198Write and solve a percent equation.Write and solve a percent equation.

A) What is 85% of A) What is 85% of 320?320?

B) 393 is 60% of B) 393 is 60% of what number?what number?

Example 5, page 199Example 5, page 199Find each number or percent.Find each number or percent.

Ex. 5a) 105 is Ex. 5a) 105 is 125% of what 125% of what number.number.

Ex. 5b) What Ex. 5b) What percent of 320 is percent of 320 is 1.6?1.6?

Ex. 5c) 640 is what Ex. 5c) 640 is what percent of 32?percent of 32?

Ex. 5d) 0.13% of Ex. 5d) 0.13% of what number is what number is 3000?3000?

Using Estimation, page 199Using Estimation, page 199Use fractions to estimate.Use fractions to estimate.

Ex. 6a) 49% of 280 Ex. 6a) 49% of 280 is what number?is what number?

Ex. 6b) What is Ex. 6b) What is 65% of 334?65% of 334?

Ex. 6c) What is Ex. 6c) What is 74.2% of 44?74.2% of 44?

Ex. 6d) 11% of 521 Ex. 6d) 11% of 521 is what number?is what number?

Example 7, page 200Example 7, page 200

A store advertises sneakers on sale for 33% off. A store advertises sneakers on sale for 33% off.

The original price of sneakers is $56.The original price of sneakers is $56. A) Estimate the amount the sneakers have been A) Estimate the amount the sneakers have been

marked down.marked down.

B) Estimate the sale price of the sneakers.B) Estimate the sale price of the sneakers.

SUMMARYSUMMARY

TO SOLVE PERCENT PROBLEMS eitherTO SOLVE PERCENT PROBLEMS either Use a percent proportionUse a percent proportion

N/100 = part/wholeN/100 = part/whole

OrOr A percent equation whereA percent equation where

““is” means = and “of” means to is” means = and “of” means to multiply.multiply.

AssignmentAssignment

P. 200 1 – 57 odd; 61 – 73 oddP. 200 1 – 57 odd; 61 – 73 odd