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.
Clue Sheet Overhead
The information you put on the overhead will lead the students to your chosen thief.
|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
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.
Clue Sheet Activity Sheet
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
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.
Apprehended in Harrisburg, PA
Monitor students' work, and listen for students who are struggling.
Students may have problems correctly answering Question 1. Some
students will leave their answers as decimals, but the suspect list
does not have decimal heights. Ask, "Do any of your answers match the
answers on the suspect list? What do you notice about the answers on
the suspect sheet?"
[They are in feet and inches.]
"So what do you have to do?"
[Convert the decimal into inches.]
The most common problem will be students' making the decimal the number
of inches, like 5.5 feet must be 5 feet 5 inches. Ask, "How many inches
are in half a foot?"
"What should the height be?"
[5 feet 6 inches.]
Remind them to multiply 12 inches by the decimal part of their answer to find the number of inches.
For Clue 4, students use their answers from Clue 3 and measure the
scale line in centimeters and use a proportion to calculate how far to
measure on the map to find the perpetrator's city. Be prepared to help
students read a ruler. Remind them that the smaller lines represents
millimeters, which are 0.1 centimeters.
Have students submit their papers when they can identify the thief.
Have students share who they think is the perpetrator. If students
disagree, have them explain why their answer is correct. Or the teacher
could ask what changes in the clues could lead to any of the other