Math Investigations

Help with Opening PDF Files

Chapter 22

Part 1: For the problem in the Teacher's Edition, page 566

Students can practice their research skills by finding the currency exchange rates of each country. Or you can provide them with the data sheet found in the Problem Worksheet (PDF file).

Ask students how they would find the amount of currency they would receive for $2.00. Since the currency exchange rate is equivalent to $1.00, adding the currency exchange rate to itself would give the amount of currency they would receive for $2.00. Some students may suggest multiplying the currency exchange rate by 2. That will also work. However, students have not learned multiplication with decimals yet. You might want to let interested students multiply with a calculator.

Answer:

Answers will vary if students look up their own data.
Answers if students use the data we provided:

CountryAmount of Currency for $2.00 (U.S.)
Algeria159.36 Algerian Dinars
Argentina6.12 Argentine Pesos
Brazil5.84 Reals
Croatia15.74 Kunas
Indonesia18,622.40 Rupiahs
Japan250.78 Yen
Rwanda950.74 Rwanda Francs
Slovakia90.66 Koruny
Turkey3014.452 Liras

Part 2: Be an Investigator

A good time to do this investigation is after Lesson 4 on adding and subtracting decimals.

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.

Ask students why they think the editor of the magazine wanted the students to round the numbers. Discuss that in an article such as this, the exact numbers are not important to know and rounded numbers make the article easier to read.

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

Doing the Investigation

When students are finished, you might want to put two groups of students together so they can share their answers. If they find any differences in their answers, have them discuss the solutions to see if they can agree on the correct one.

Answers:

Here are the statements about Brazil and Argentina with the numbers rounded.

Argentina
The area of Argentina is about 2.8 million square kilometers.
The population of Argentina is about 38.3 million people.
There are about 8.0 million telephone lines in use in Argentina.
The average person in Argentina lives to be about 75 years old.
The average age of the people in Argentina is about 29 years.
There are about 7 million cell phones in use in Argentina.

Brazil
The area of Brazil is about 8.5 million square kilometers.
The population of Brazil is about 179.9 million people.
There are about 38.8 million telephone lines in use in Brazil.
The average person in Brazil lives to be about 71 years old.
The average age of the people in Brazil is about 27 years.
There are about 35 million cell phones in use in Brazil.

Here are all of the differences I found between Brazil and Argentina.
The difference in area between Brazil and Argentina is about 5.7 million square kilometers.
The difference in population between Brazil and Argentina is about 141.6 million people.
The difference in telephone lines in use between Brazil and Argentina is about 30.8 million telephone lines.
The difference in age lived to by the average person in Brazil and Argentina is about 4 years.
The difference in average age of the people in Brazil and Argentina is about 2 years.
The difference in the number of cell phones between Brazil and Argentina is about 28 million cell phones.

Student Report

The student report gives students an opportunity to show what they have done.

Extending the Investigation

Have the students do more research on Argentina and Brazil and write an article about the two countries. Have them round the numbers they use in the article.


Houghton Mifflin Math Grade 4