a ratio can have equivalent ratios just like a fraction can have equivalent fractions

If you know the ratio of students to teachers is 5 to 1 and you know there are 15 teachers, is there a way to figure out

the number of students?

In this lesson you will learn to solve for missing values in a

ratio problem by using multiplicative reasoning

Let’s Review

A ratio can have equivalent ratios just like a fraction can have equivalent

fractions.

2 : 1x3 x3 6 : 3

A Common Mistake

The ratio of students to teachers is 5 to 1. There are 15 teachers.

5

1

wrong row!students

teachers

15

?

Core Lesson

Andy has a ratio of books to DVDS of 3 : 2 in his room. If he has 15 books, how many

DVDs does he have?

How can I use the ratio to help set up

and solve?

Core Lesson Books to DVDs3 to 2

15 books? DVDS

Ratio Actual

3

2

Books

DVDs

15

? How many groups of books does Andy have?

Core Lesson

x 5

x 5

Ratio Actual

3

2

Books

DVDs

15

?? = 10 DVDs

In this lesson you have learned to solve for missing values in a

ratio problem by using multiplicative reasoning.

Guided Practice

Anita collects shells and stones in a ratio of 1 : 2. If she has a total of 6 shells, how many stones does she have?

Extension Activities

Create a flipbook with your own ratio problem and illustrations showing how to solve it using

multiplicative reasoning.

Extension ActivitiesAnnie bakes cookies and cupcakes in a ratio of 2 to 7 for her gift boxes. Her school needs 36 desserts to sell in a bake sale.

How many cupcakes will she bake?

How many cookies will she bake?

Create an illustration and a table to support your work. Explain the multiplicative reasoning used.

Quick Quiz

George buys oranges and apples at a ratio of 2 :5 for his party. If he has 10 oranges, how many apples does he have?Kelly bakes cupcakes and cookies in a ratio of 5 to 3 for her bakery. If on any given day she bakes 15 cookies, how many cupcakes did she bake that day?