“Cross Multiply and Divide”Can be used to determine the unknown value in any proportional reasoning problem

For example….

1110

=𝑎60 Multiply these two

60 x 11 = 10 x a

660 = 10 x a And now divide by 10

660 ÷ 10 = a

66 = a

Try these….

53=𝑛24

47=𝑚35

1821

=𝑟14

A recipe for salad dressing uses 60 mL of vinegar for 240 mL of oil. Emily has only 40 mL of vinegar.

How much oil should she use?

Lesson 3: Unit Rates

• A rate is a ratio that is used to compare different kinds of quantities

• A unit rate describes how many units of the first type of quantity equals one unit of the second type of quantity

• Some common unit rates are….– miles (or kilometers) per hour (km/h)– earnings per hour ($/h)– Can you think of any….?

What is the difference between a ratio and a rate?

RATIO

Definition Facts/Characteristics

Examples Non-Examples

RATE

Definition Facts/Characteristics

Examples Non-Examples

How can we determine the best deal?

Which box is the better deal?

Determine the price for 100g for each box.

Which is the better buy?

Lesson 3: Unit Rates

Homework/Practice

Pg. 123 # 1 - 9