SETTING UP A PROPORTION

SPI 6.1.1 Predictions & ConjecturesSPI 6.2.6 Rates & Percents

What is a proportion?

A proportion is 2 equivalent ratios.Example: 6 = 3

20 10

What is a ratio? A ratio is a comparison of two numbers

by division.Example: 6 black socks to a total of 20 socks

Using Proportions to solve Predictions

Out of the 32 students in a health class, 24 prefer using gel toothpaste. Based on these results, how many of 500 students in the school can be expected to prefer using gel toothpaste?Ratio: prefer gel toothpaste

total students in class

Answer: 375 students out of 500 prefer gel toothpaste

PARTTOTAL

Using Proportions to solve Ratios

At West Boulevard Middle School, the teacher to student ratio is 3 to 78. If there are 468 students enrolled at the school, how many teachers are there at the school?

Answer: 18 teachers to 468 students

Proportions to solve Percent of a Number

The Mooney High School football team won 75% of their football games. If they played 12 games, how many did they win?

Answer: won 9 games out of 12 total games

Setting Up a Proportion

Suppose you buy 2 CDs for $21.99. How many CDs can you buy for $65.97?

Answer: 6 CDs for $65.97

Using Proportions to solve Discounts

A skateboard is on sale for 85% of the regular price. If it is regularly priced at $40, how much is the sale price?

How much is the discount?

Answer: $34 sale price

Answer: $6 discount

Using a Proportion to solve Unit Rate

If you work 22 hours a week and earn $139.70, how much money do you earn per hour?

Answer: You earn $6.35 every hour

Proportions to solve Percent of a Number

Chad and Alisa donated 30% of their book collection to a local children’s hospital. If they had 180 books, how many did they donate to the hospital?

Answer: 54 children's books out of 180 books total

Proportions to solve Probability

Lorenzo asked every tenth student who walked into school to name their favorite pizza topping.

1) What is the probability that a student will prefer pepperoni pizza?

2) There are 384 students at the school Lorenzo attends. Predict how many students prefer pepperoni pizzas.

Favorite Pizza Topping

Topping Students

Pepperoni 18

Cheese 9

Sausage 3

Mushroom

2Answer: 18/32

Answer: 216 prefer pepperoni pizzas

Proportions to solve Predictions Use the results shown

to predict the number of people out of 300 that would prefer vanilla ice cream?

Favorite Ice Cream

Flavor Amount

Vanilla 9

Chocolate 8

Strawberry

3

Answer: 135 prefer vanilla ice cream

Using Proportions to solve Discounts

The regular price of a pair of sneakers is $40. The sale price is 17% off the regular price. What is the sale price?

Answer: The sales price of the sneakers is $33.20