Ratios and Unit Rates.

Presentation on theme: "Ratios and Unit Rates."— Presentation transcript:

Ratios and Unit Rates

Ratio – a comparison of two quantities by division
Ratios can be written in three ways: 1) as a fraction in simplest form 2) with the word “ to ” 3) with a colon “ : ”

Examples: Four out of five dentists surveyed recommend sugarless gum for their patients who chew gum to :5 5 9 people out of 20 like chocolate ice cream to :20 20

In a class of thirty students, thirteen are boys
In a class of thirty students, thirteen are boys. Write a ratio for the number of boys to students in the class. 13/ to :30 Write a ratio for the number of boys to the number of girls. 13/ to :17

Out of 100 students, 40 said they had afterschool jobs
Out of 100 students, 40 said they had afterschool jobs. Write a ratio for the number of students who had jobs to the number who did not. 40/60 = 2/3 40 to 60 = 2 to :60 = 2:3

24 questions correct on a 100-question test
6 freethrows made out of 10 attempts 6/10 = 3/ to : 5 24 questions correct on a 100-question test 24/100 = 6/ to : 25 5 cookies eaten out of 20 cookies 5/20 = ¼ to : 4

Unit Rate – a rate for “one” of something; a ratio with a denominator of 1.
If three bananas cost \$1.89, how much does one banana cost? \$1.89/3 = .63/1 banana

Examples: You need to buy soda for a party. The store sells packs for \$ Find the unit rate for one 12-pack? \$7.80/3 = \$2.60/1

You travel 300 miles in five hours. Find the unit rate per hour.
300/5 = 60 miles/1 hour A girl can jump rope 200 times in 4 minutes. What is the unit rate per minute? 200 / 4 = 50 times/1 minute

Determine which is the better buy:
You need to buy pizzas for a class party. You can buy 4 large pizzas for \$10.00, or you can 7 large pizzas for \$ Which is the better buy? \$10.00 / 4 = \$2.50/1 \$19.25 / 7 = \$2.75/1 It is cheaper to buy 4 pizzas.