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Ratios and Proportions

Ratios and Proportions. Created by: Mrs. J Couch. Ratio. A ratio is a comparison of two numbers or quantities. part to part part to whole whole to part A ratio can be expressed three ways : Using the fraction bar as in ⅔ Using a colon symbol as in 2:3

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Ratios and Proportions

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  1. RatiosandProportions Created by: Mrs. J Couch

  2. Ratio • A ratio is a comparison of two numbers or quantities. • part to part part to whole whole to part • A ratio can be expressed three ways: • Using the fraction bar as in ⅔ • Using a colon symbol as in 2:3 • Using the word “to” as in 2 to 3.

  3. Writing Ratios • Write each ratio using the other two ways: • The ratio of 3 inches to 20 feet. • The ratio of 26 students: 1 class • The ratio of 2 boys/3 girls

  4. Equivalent Ratio • Write an equivalent ratio for the following: • 12:13 • 6 to 8 • ¾

  5. Simplifying Ratios • Write each ratio in simplest form: • 15:20 • 2 to 6 • 10/50

  6. Ratio Write a ratio for each of the following:

  7. Practice • http://studyjams.scholastic.com/studyjams/jams/math/algebra/ratio.htm

  8. Tables • The table below shows the number of each item sold at the concession stand. • What might the ratio 2:1 represent?

  9. Tables • The table below shows the number of each item sold at the concession stand. • What might the ratio 3 to 2 represent?

  10. Proportions • A proportion is when two ratios are equivalent. 10 = 4 5 2 You can solve for an unknown value in a proportion by cross multiplying. 12 = 4 x 2 12= 4 x 2 Cross multiply 4*X = 12*2 Multiply the side with 2 #s 4*X = 24 Use inverse operation of multiply divide both sides by 4 ÷4 ÷4 X = 6

  11. Study Jams • http://studyjams.scholastic.com/studyjams/jams/math/algebra/proportion.htm

  12. Proportions/Guided Practice You can solve for an unknown value in a proportion by cross multiplying. 16 = X 4 2 16= X 4 2 Cross multiply 4*X = 16*2 Multiply the side with 2 #s 4*X = 32 Use inverse operation of multiply divide both sides by 4 ÷4 ÷4 X = 8

  13. Proportions/Guided Practice You can solve for an unknown value in a proportion by cross multiplying. 3 = 24 2 x 3= 24 2 x Cross multiply 24*2 = 3*X Multiply the side with 2 #s 48 = 3*X Use inverse operation of multiply divide both sides by 3 ÷3 ÷3 16 = X

  14. Practice • Determine the missing value.

  15. Proportions • Rusty drives his race car at a constant speed of 150 miles per hour. Which method can be used as the first step to find the number of hours it will take him to drive 300 miles? • A. Divide 300 by 150. • B. Multiply 300 by 150. • C. Subtract 300 from 150. • D. Add 300 to 150.

  16. Exit Slip 1. Simplify the ratio 4 to 20 2. Write the ratio 1:2 in two other forms 3. Solve for the missing value in the proportion: 12 = X 4 3

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