Ratiosand

Word Problems with Ratios

Skill MaintenancePage 55

Commutative Property

• Addition 3 + 4 = 4 + 3 5 + 17 + 43 = 17 + 43 + 5

• Multiplication 3 * 4 = 4 * 3 2 * 7 * 8 = 8 * 2 * 7

Substitution

• Important concept when working with variables

• Substitution: Replace a variable with a number value

Ratios

• Ratio: Compares two numbers• We can write a ratio as

–1 to 3–1:3–1/3

We often use ratios in cooking. A recipe calls for one cup of sugar and two cups of flour. The ratio of sugar to flour is

one to two.

We can also use ratios in painting. Let’s say we need to mix three cans of blue paint and one can of white. The ratio

of blue to white is three to one.

We might use ratios to make comparisons in the classroom Let’s say there are six boys and eighteen girls in the class.

The ratio of boys to girls is six to eighteen.

Why can’t we call them fractions?

• A ratio can:– Represent a part-to-whole relationship– Describe two parts of a whole relationship

• Fraction is a special type of ratio (part-to-whole)

Ratio Examples

Ratio Examples

Ratio Examples

Ratio Examples

Ratio Examples

Ratios

• Fractions are always part-to-whole relationships.

• Ratios may be part-to-whole relationships OR they can be part-to-part relationships.

Group Card Activity

Group Card Activity• Write the following ratios in two ways and

tells us if it is a part-to-part or part-to-whole ratio:– Hearts to Diamonds– Spades to all cards– Face cards to Non-face cards– Odd numbered cards to all cards– Make up two of your own

• One part-to-whole• One part-to-part

Word Problems Using Ratios

• Break Problem into small steps• Step 1: Label the ratio we are looking for• Step 2: Think about the numbers for our

ratio.• Step 3: Use the numbers we found to set

up the ratio.

Problem-Solving ActivityPage 57

HomeworkPages 147 and 148

All ActivitiesAll Problems