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## Highway Robbery

• Lesson
6-8
1

The National Bank of Illuminations has been robbed! Students apply their knowledge of ratios, unit rates, and proportions to sort through the clues and deduce which suspect is the true culprit.

In this lesson, students assume the role of a detective investigating a bank robbery. Students wear police badges from a party store or that you make, and use four clues to help them apprehend the thief.

Below is a suspect matrix with the clue values needed to make a particular suspect the actual thief. Before class, choose one, and fill in the blanks on the Clue Sheet Overhead.

Suspect Matrix

 Roy G. Biv Jen Eric Matthew Matics Clue 1 Question 1: 15 cm Clue 1 Question 1: 13.2 cm Clue 1 Question 1: 15 cm Clue 2 Question 2: 25 pounds Clue 2 Question 2: 25 pounds Clue 2 Question 2: 32 pounds Clue 3 Question 5: 16 miles/gallon Clue 3 Question 5: 9 miles/gallon Clue 3 Question 5: 8 miles/gallon Polly Hedron Evan Number Al T. Tude Clue 1 Question 1: 13.2 cm Clue 1 Question 1: 13.2 cm Clue 1 Question 1: 15 cm Clue 2 Question 2: 32 pounds Clue 2 Question 2: 25 pounds Clue 2 Question 2: 32 pounds Clue 3 Question 5: 8 miles/gallon Clue 3 Question 5: 25 miles/gallon Clue 3 Question 5: 16 miles/gallon
The Suspect List Activity Sheet summarizes what is known about each person.
You can also create your own suspect list, using people you make up or people you know, such as other teachers or classmates. Having two or three possible values for each characteristic makes it easier to have students find suspects to match their calculations.

Give each student a pretend police badge as they enter the classroom. You can find them at most party stores, or make them yourself. Address the class as if they are a police academy with an opening statement like, "Detectives, we have received an urgent email from the captain of police. We have been chosen for this task because of our superior math skills. I have created a copy of the note for everyone."

Give students the option of working in pairs or individually. Groups larger than two tend to result in students being off-task with an unequal distribution of work.

Pass out the Clue Sheet Activity Sheet to each student and place the Clue Sheet Overhead on the board.

Lead a class discussion about the clues. Ask, "What they would do with ___ pounds of quarters?" or "If the perpetrator's car gets ___ miles per gallon, do you think he/she is very far away?" Some students, especially students whose first language is not English, may not be familiar with the vocabulary words perpetrator, apprehend, and deduction. As you read the letter, pause to ask for volunteers who can define each of these words.

• Perpetrator- a person who committed the crime
• Apprehend- to arrest someone
• Deduction- to reach a conclusion
Then, have students fill in the blanks in Questions 1, 2, and 5.

Review conversions that students will need to solve problems: 12 inches in 1 foot, 4 quarters in 1 dollar. Suggest that students write word ratios to write a proportion. For example, Question 1 compares the centimeters in the photo to the inches in reality. A word ratio would be photo/real or centimeters/inches. Remind students that for these word ratios, all "photo," or "centimeter," measurements must be in the numerator. All "real," or "inch," measurements must be in the denominator.

Be conscious that proportions are not required to solve Questions 3, 4 or 5. Alternate solution methods can lead to the correct results, so if you want students to use proportions, clearly state so.

Pass out the Suspect List Activity Sheet. Read the Question 1 of the suspect list out loud with the class and let them know that they can work with both the clue sheet and suspect list at the same time to find the perpetrator.

### Common Core State Standards – Practice

• CCSS.Math.Practice.MP1
Make sense of problems and persevere in solving them.
• CCSS.Math.Practice.MP2
Reason abstractly and quantitatively.
• CCSS.Math.Practice.MP4
Model with mathematics.
• CCSS.Math.Practice.MP5
Use appropriate tools strategically.
• CCSS.Math.Practice.MP7
Look for and make use of structure.