Lecture Proportions: Word Problems

Proportions: Word Problems

How to use Proportion to solve every day word problems

Math Technique: Cross Multiplication

*Cross multiply method can be used to find the missing value of a proportion

*Multiply diagonally & set each cross equal to each other. Then, divide both sides by the value with the variable. This will give the answer to a true proportion.

How to set up to show Equialence in Proportions

When there are units of measure, the same units should be across from each other in the proportion.

*Notice the units of measurement are alike directly across from the other value.

Example: Set the Proportion from the given Ratios

Scenario: 34 buttons to 3 shirts is equal to 11.5 buttons to 1 shirt.

*Put these into fraction form and set them up as equivalent proportions.

What do you notice about the units of measurement?

Practice:

• First, understand the correct set up of the ratios in proportion will help when solving word problems.

• Example: If 6 melons cost $9; What is the cost of 10 melons?

• What do you know? the cost of 6 melons is $9 and it is equally proportioned to 10 melons to X dollars.

• Now set up the proportion and solve to find the total cost of 10 melons.

Answer to the Melon Word Problem:

How did you do?

Multiple Choice

Solve for X

• 1/10

• 4

• 5

• 10

Multiple Choice

If four ice creams cost $3.20, what would 8 ice cream cost?

• $6.40

• $7.20

• $9.60

• $10.00

Multiple Choice

A cake recipe calls for 1.5 cups of milk and 3 cups of flour. Jake made a mistake and used 5 cups of flour. How many cups of milk should he use to keep the proportions correct and equal?

• 2.5 cups milk

• 2 cups of flour

• 1.75 cups milk

• 2.25 cups milk

Multiple Choice

A scale model of a whale is being built. The actual length of the whale is 65 feet. The scale of the model is 2 in : 3 ft. What will be the length of the model?

• 97.5 inches

• 41.56 inches

• 30.6 inches

• 43.33 inches

Multiple Choice

About 13 out of 20 homes have personal computer. On a street with 60 homes, how many computers would you expect to have?

• 4.5 homes

• 39 homes

• 4.3 computers

• 39 computers

Multiple Choice

Hamburger meat sells for $6.00 for every 3 pounds. If Alicia buys 10 pounds of hamburger meat, how much will she pay?

• $10.00

• $20.00

• $30.00

• $60.00

Multiple Choice

12 ounce shampoo bottle lasts MIke 16 weeks. How long would you expect an 18 ounce bottle of the same brand to last him?

• 6 weeks

• 20 weeks

• 24 weeks

• 30 weeks

Multiple Choice

Pat needs 14 sticks of pepperoni to make 28 pizzas. How many sticks of pepperoni are needed to make 36 pizzas?

• 18 pizzas

• 18 sticks

• 15 pizzas

• 252 sticks

Geometry uses Proportions by solving similar figures.

Example: The pair of figures is similar. Find the missing side.

Multiple Choice

The pair of figures is similar. Find the missing side.

• x = 9

• x = 13

• x = 4

• x = 36

Geometry Proportion Example:

The pair of figures is similar. Find the missing side.

Multiple Choice

The pair of figures is similar. Find the missing side.

• x = 20

• X = 5

• x = 12

• x = 4

Multiple Choice

A rectangular garden is 45 ft wide and 70 ft long. In a drawing, the width is 9 in. Identify the length on the drawing.

• 7 inches

• 9 inches

• 12 inches

• 14 inches

Multiple Choice

An 8 foot tall street sign cast a 6 foot shadow at the same time that a building casts a 48 foot shadow. How many feet tall is the building?

• 36

• 54

• 64

• 96

• 144

Multiple Choice

If the man in the diagram is 6 feet tall, what is the height of the tree?

• 4

• 20

• 24

• 36

• 96