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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 15 Page 188

Use the portion where both values are known.

Calories	20	80	10	90
Miles	1/6	2/3	1/12	3/4

Equivalent Ratios: 20: 16, 80: 23, 10: 112, and 90: 34.

Practice makes perfect

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

Calories	20		10	90
Miles	1/6	2/3

We know that we burn 20 calories in 1/6 miles. Let's write this as a ratio. 20calories/16miles or 20/16

We will use this rate to find the missing values.

First Value

We can find an equivalent ratio with a denominator of 23 to find how many calories we burn in 23 miles.

20/16

a/b=a * 4/b * 4

20* 4/16* 4

Multiply

80/23

We burn 80 calories in 23 miles.

Calories	20	80	10	90
Miles	1/6	2/3

Second Value

Now, we can find an equivalent ratio with a numerator of 10 to find how many miles we travel to burn 10 calories.

20/16

a/b=.a / 2./.b / 2.

20÷ 2/16÷ 2

Calculate quotient

10/112

We burn 10 calories in 112 miles.

Calories	20	80	10	90
Miles	1/6	2/3	1/12

Third Value

Now, we can find an equivalent ratio with a numerator of 90 to find how many miles we travel to burn 90 calories.

10/112

a/b=a * 9/b * 9

10* 9/112* 9

Calculate quotient

90/34

We burn 90 calories in 34 miles.

Calories	20	80	10	90
Miles	1/6	2/3	1/12	3/4

The equivalent ratios are 20: 16, 80: 23, 10: 112, and 90: 34.

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