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Proportions, Ratio, Rate and Unit Rate Review. Ratio. What is a ratio? A ratio is a comparison between two numbers. What is an example of a ratio? There are 15 boys in a class and 8 girls. A ratio to represent the class would be 15 : 8, 15 to 8 and 15 8
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Ratio • What is a ratio? • A ratio is a comparison between two numbers. • What is an example of a ratio? • There are 15 boys in a class and 8 girls. A ratio to represent the class would be 15 : 8, 15 to 8 and 15 8 • You drove 30 miles in 45 minutes. A ratio to represent this situation is 30 : 45, 30 to 45 and 30 45 • Order DOES matter in a ratio!!! 4 : 5 is NOT the same as 5 : 4
Ratio • How do you find equivalent ratios? • To find an equivalent ratio multiply the numerator and denominator by the SAME number. • What is an example of equivalent ratios? • You are given the ratio 4 5 • To find an equivalent ratio multiply the top and bottom by the SAME number. I am going to use 2 • 4 x 2 = 8 5 x 2 10
Rate • What is a rate? • A rate is a ratio with 2 different units (measurement) • What is an example of a unit? • You ran 5 miles in 2 hours. A rate to represent you running would be 5 miles 2 hours • 5 apples cost $2.00. A rate to represent the cost of the apples would be $2.00 5 apples • REMEMBER – ALWAYS put money in the numerator!
Unit Rate • What is a unit rate? • A unit rate is a rate with a denominator of 1. • Do unit rates of two different units? • YES, unit rates are rates and rates have two different units! • How do we find unit rate? • 1st: Set up a unit rate • 2nd: Divide by the denominator • 3rd: Write your answer in word form (the numerator PER the denominator).
Unit Rate • What is an example of a unit rate? • A car drives 30 miles on 10 gallons. To write a unit rate follow the three step. • 1st: Set up a rate 30 miles 10 gallons • 2nd: Divide by the denominator 30 miles ÷ 10 = 3 miles 10 gallons ÷ 10 1 gallon • 3rd: Write in word form 3 miles per gallon
Proportion • What is a proportion? • Proportions are two ratios set equal to each other. • What is an example of a proportion? • Since a proportion are 2 equal ratios an example could be: • 4 = 8 5 10 • How do you know if it is a true proportion? • The cross-products of the ratios must be equal. • 4 x 10 = 40 and 5 x 8 = 40 It is a proportion!
Proportion • When a proportion contains a variable, how do you solve for the variable? • To solve for the variable you cross multiply! • Example: 6 = x 10 30 30(6) = 10x 180 = 10x 18 = x
Proportion • Now lets try write and solving a proportion. • There is a ratio of 8 boys to 12 girls in a classroom. How many girls would there be if there were 12 boys in the classroom?
Proportion • If given a ratio how can you form a proportion? • If given a ratio you can form a proportion by finding an equivalent ratio and setting them equal to each other. • Given the ratio 2 to 3 form a proportion.