Math Investigations

Help with Opening PDF Files

Chapter 14

Part 1: For the problem in the Teacher's Edition, page 332

Students can practice their research skills by researching information about surfboards, or you can provide them with the data sheet that shows information about surfboards found in the Activity Page (PDF file).

To make sure the students understand the decimals they are using, ask questions such as:

  • Is a surfboard that is 2.4” thick, less than 2 1/2 inches thick or more than 2 1/2 inches thick? (less than 2 1/2 inches thick)

Create a bulletin board of the surfboard ads that students create.

Answers will vary.

Part 2: Be an Investigator

A good time to do this investigation is after Lesson 7 on dividing a decimal by a decimal.

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.

You might want to introduce this investigation using an example with whole numbers. Say Suppose a surfboard is nine feet long and the fish it is named after is three feet long. How would you find out how many times longer the surfboard is than the fish? (Divide nine by three.) How many times longer is the surfboard than the fish? (Three times longer.)

Ask What division problem would you solve to find out how many times longer the Jawfish Surfboard is than the Jawfish? (1.82 ÷ 0.13) Then let students work on their own.

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

Doing the Investigation

Suggest to students that they multiply to check to see if their answer is correct. For example, suppose they calculate that the Jawfish Surfboard is 14 times longer than a Jawfish. They could multiply 14 by 0.13 meters. If they are correct they should get an answer of 1.82 meters.

Answers for the Data Sheet

Surfboards by The Dude

Tropical Fish Name for Surfboard Length of Fish (meters) Length of Surfboard (meters) __ Times the Length of the Fish
Jawfish 0.13 meters 1.82 meters 14
Firefish 0.06 meters 2.1 meters 35
Goby 0.03 meters 2.1 meters 70
Hawkfish 0.07 meters 2.03 meters 29
Butterflyfish 0.15 meters 2.1 meters 14

Student Report

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

Extending the Investigation

Have the students actually create the ads for these surfboards.


Houghton Mifflin Math Grade 5