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Learn how to solve proportions and apply them to various problems. Explore the concept of cross-multiplication and practice writing and solving proportions. Homework included.
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Today’s Agenda 1. Lesson: Proportions • Quiz 7 back • Homework
6-2 Proportions Objectives: • Solve proportions • Use proportions to solve problems
Understanding Proportion • A Proportion is an equality of two ratios. • The proportion a/b = c/d is read as “a is to b as c is to d.” • A proportion has two cross products a * d, and b * c. The process of forming cross products is called cross multiplying.
Write the verbal description as a proportion • The proportion a/b = c/d is read as “a is to b as c is to d.” Write • 7 is to x as 14 is to 20 • n is to 9 as 10 is to 18 • 35 is to 25 as p is to 5
Use cross products to tell whether the two ratios are equal 2 and 12 4 and 6 3 16 16 21
Solve the Proportion • In many proportion problems, one of the numerators or one of the denominators is a variable. Here is an example: 8/x = 2/3 • To solve this, you use the cross multiplication • Solve the proportion 8/x = 2/3 • Write the original problem • Use cross multiplying • Divide each side by 2 • Simplify
Solve the Proportion Solve x/12 = 18/27
Solve the Proportion Solve 4/3 = b/21
Solve the Proportion Solve x/12 = 18/27
Solve the Proportion Solve 7/9 = j/22.5
6-3 Writing Proportions • Here, you will read a word problem and come up with your own proportions. Then, you will solve the proportion as learned yesterday. • You must make sure that proportion is written in the correct order. • Three posters cost $9.60. At that rate, how many posters can you buy for $48?
Writing and Solving Proportions • At the Copy Shoppe, 18 copies cost $1.08. At that rate, how much will 40 copies cost?
Writing and Solving Proportions • A microchip inspector found three defective chips in a batch containing 750 chips. At that rate, how many defective chips would there be in 10,000 chips?
6-2 Proportions Objectives: • Solve proportions • Use proportions to solve problems
Solve the Proportion • Solve the proportion x/12 = 1/4 • Write the original problem • Use cross multiplying • Divide each side by the number before the variable 4. Simplify
Writing and Solving Proportions • When wheel B turns 2 revolutions, wheel A turns 5 revolutions. When wheel A turns 40 revolutions, how many revolutions does wheel B turn?
Writing and Solving Proportions • It takes a machine 12 minutes to fill 200 bottles of soda. At this rate, how many minutes will it take the machine to fill 500 bottles of soda?
Writing and Solving Proportions • A car gets 24 miles per gallon of gasoline. How many gallons of gasoline would the car need to travel 144 miles?
Writing and Solving Proportions • Jerry read a 200-page book in 10 hours. At that rate, how long will it take him to read a 320-page book?