2-6 Ratios and Proportions Algebra 1 Glencoe McGraw-Hill Linda Stamper

A ratio compares two quantities by division! A ratio is a comparison of two quantities measured in the same unit. A ratio compares two quantities by division! You can write a ratio in different ways. 5 to 6 5 : 6 The order of the numbers in a ratio is very important. The first number in a ratio always names the quantity mentioned first.

An equation that states that two ratios are equal is a proportion. Cross Product Property If two ratios are equal then their cross products are also equal. Determine whether each pair of ratios forms a proportion. Write yes or no (must show support work). yes

Determine whether each pair of ratios forms a proportion Determine whether each pair of ratios forms a proportion. Write yes or no (must show support work). Example 1 Example 2 no no

Write the cross products. When a proportion involves a variable, solving for the variable is called solving the proportion. Solve the proportion. Check Write the cross products. Multiply. Solve Do the arithmetic work off to the side or make a separate column for this work! 

/ / Solve the proportion. Check Write the cross products. Multiply. 5 Check / Write the cross products. / 12 Multiply. Solve You can not cross cancel through an equal sign.

Solve the proportion. If necessary, round to the nearest hundredth. Example 3 Example 4 Example 5 Do the arithmetic work off to the side or make a separate column for this work! You can simplify a fraction before you use cross products.

Solve the proportion. Example 6 Example 7 Example 8

Write a proportion for the problem. Then solve. Mrs. Jones travels 140 miles in 2.5 hours. At this rate, how far will she travel in 4 hours? Start with a word ratio. Mrs. Jones will travel 224 miles in 4 hours.

Mrs. Jones travels 140 miles in 2. 5 hours Mrs. Jones travels 140 miles in 2.5 hours. At this rate, how long will it take her to travel 224 miles? Write word ratio. Mrs. Jones will travel 224 miles in 4 hours.

Write a proportion for each problem. Then solve. Example 9 A mechanic charged $92 for 4 hours of work. At this rate, how much will be charged for 6 hours? Example 10 Mr. Green used 3 gallons of paint to cover 1,350 sq ft. At this rate, how much paint will be needed to cover 1,800 sq. ft.? Example 11 The ratio of football players to cheerleaders in the NFL is 48 to 6. If there are 1,440 football players, how many cheerleaders are there? Example 12 Sue, the speed reader, can read 12 pages in 4.5 minutes. At that rate, how many pages will she read in 60 minutes?

Example 9 The mechanic will charge $138 for 6 hours of work. Example 10 Mr. Green will need 4 gallons of paint. Example 11 There are 180 cheerleaders. Example 12 Sue will read 160 pages.

The mechanic will charge $138 for 6 hours of work. Example 9 A mechanic charged $92 for 4 hours of work. At this rate, how much will be charged for 6 hours? Write a word ratio. Sentence. The mechanic will charge $138 for 6 hours of work. Do the arithmetic work off to the side or make a separate column for this work!

Example 10 Mr. Green used 3 gallons of paint to cover 1,350 sq ft Example 10 Mr. Green used 3 gallons of paint to cover 1,350 sq ft. At this rate, how much paint will be needed to cover 1,800 sq. ft.? Write word ratio. Mr. Green will need 4 gallons of paint.

Example 11 The ratio of football players to cheerleaders in the NFL is 48 to 6. If there are 1,440 football players, how many cheerleaders are there? Write word ratio. There are 180 cheerleaders.

Example 12 Sue, the speed reader, can read 12 pages in 4. 5 minutes Example 12 Sue, the speed reader, can read 12 pages in 4.5 minutes. At that rate, how many pages will she read in 60 minutes? Sue will read 160 pages.

Homework 2-A11 Pages 109-110 #9-33,41-48.