Ratios and Word Problems with Ratios

Skill Maintenance Page 55

Commutative Property Addition  =  = 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

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

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 Activity Page 57

Homework Pages 147 and 148 All Activities All Problems