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Big Ideas Math: Modeling Real Life, Grade 7

BI

Big Ideas Math: Modeling Real Life, Grade 7 View details

1. Ratios and Ratio Tables

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Exercise 18 Page 188

Use the portion where both values are known.

Tea (cups)	3.75	2.5	8.75	6.25
Milk (cups)	1.5	1	3.5	2.5

Equivalent Ratios: 3.75:1.5, 2.5:1, 8.75:3.5, and 6.25:2.5

Practice makes perfect

We want to complete a table. We can use the portion where both values are known to find the missing values.

Tea (cups)	3.75
Milk (cups)	1.5	1	3.5	2.5

We know that for each 3.75 cups of tea we add 1.5 cups of milk. Let's write this as a ratio. 3.75cups of tea/1.5cups of milk or 3.75/1.5

We will use this rate to find the missing values.

First Value

We can find an equivalent ratio with a denominator of 1 to find how much tea we use for 1 cup of milk.

3.75/1.5

a/b=a * 23/b * 23

3.75* 23/1.5* 23

Multiply

2.5/1

We found that we add 2.5 cups of tea for each 1 cup of milk.

Tea (cups)	3.75	2.5
Milk (cups)	1.5	1	3.5	2.5

Second Value

Now, we can find an equivalent ratio with a denominator of 3.5 to find how much tea we use for 3.5 cup of milk.

3.75/1.5

a/b=a * 73/b * 73

3.75* 73/1.5* 73

Multiply

8.75/3.5

We found that we add 8.75 cups of tea for each 3.5 cup of milk.

Tea (cups)	3.75	2.5	8.75
Milk (cups)	1.5	1	3.5	2.5

Third Value

Finally, we can find an equivalent ratio with a denominator of 2.5 to find how much tea we use for 2.5 cup of milk.

3.75/1.5

a/b=a * 53/b * 53

3.75* 53/1.5* 53

Multiply

6.25/2.5

We found that we add 6.25 cups of tea for each 3.5 cup of milk.

Tea (cups)	3.75	2.5	8.75	6.25
Milk (cups)	1.5	1	3.5	2.5

The equivalent ratios are 3.75:1.5, 2.5:1, 8.75:3.5, and 6.25:2.5.

Subchapter links

Try It p.184-185

Self-Assessment for Concept & Skills p.185

Self-Assessment for Problem Solving p.186

Review & Refresh p.187

Concept, Skills, & Problem Solving p.187-188