## Chapter 18

### Part 1: For the problem in the Teacher's Edition, page 482

Provide students with a copy of the Activity Page (PDF file).

Put students in groups of four. Tell each group to make a collection of something. Then tell them to write as many ratios as they can to describe their collection. You might want to show an example by making a collection of things you write with. One ratio might be the ratio of the number of pens to the number of pencils. A good time to do this activity is after Lesson 1 on ratio.

Answers will vary.

### Part 2: Be an Investigator

A good time to do this investigation is after Lesson 3 on rates.

#### Materials

- calculators (optional)

#### Introducing the Investigation

Introduce the investigation by reading aloud the assignment at the top of the first page of the Description of Investigation and Student Report (PDF file), by having one of your students read aloud the assignment, or by having the students read the assignment individually.

Put students in groups of two to four to work on the investigation.

#### Doing the Investigation

You might want to allow your students to use calculators, but this is optional.

When students have finished the activity, have them discuss their results and share the names they gave the robots. Some students may think that Robot E is the fastest since it traveled the farthest. By calculating the speed per minute they can see that Robot C traveled the greatest distance in the same amount of time (one minute).

### Data Sheet

#### Answers:

Robot | Distance Walked | Time | Speed |
---|---|---|---|

Robot A Name: Answers will vary. |
300 feet | 5 minutes | 60 feet per minute |

Robot B Name: Answers will vary. |
2,000 feet | 4 minutes | 500 feet per minute |

Robot C Name: Answers will vary. |
1,760 feet | 2 minutes | 880 feet per minute |

Robot D Name: Answers will vary. |
1,290 feet | 3 minutes | 430 feet per minute |

Robot E Name: Answers will vary. |
2,100 feet | 3 minutes | 700 feet per minute |

The fastest robot is Robot C.

#### Student Report

The letter back to Richard Sanchez gives students an opportunity to show what they have done.

#### Extending the Investigation

Have the students walk as fast as they can and calculate their own walking speed.