Surf For More Math

Chapter 6: Addition and Subtraction of Integers

Mystery Elevation

INTRODUCTION

As you were standing at the top of a hill or a mountain, have you ever asked yourself, “How high up an I”? To answer this question, you would need to know your elevation. Elevation is the height of something like a mountain or a town in relation to a reference point, usually sea level.

THE TASK

Using the World Wide Web, you will find data on the elevation of ten different points or locations in the world. You will choose two of these points of elevation to be your mystery elevations. You will make up five operations for each of your mystery elevations, which another person can use to find to the correct integer (elevation). The answer to the first operation will become the starting point for the second operation and so on. For example, if you only had to make up two operations and your mystery elevation was -167 m you might write:
First operation: -12 + (-150) = ?
Second operation: (answer from the first operation) – (+5) = ?

THE PROCESS

Visit the following websites and choose 10 points of elevation.

Nation Master - Lowest Elevations

Nation Master - Highest Elevations

World Land Areas and Elevations

Exxun - Elevation Extremes
Statistics Canada

Your points should include the following:
· the highest elevation in the province you live in
· the highest elevation in the world
· the lowest elevation in the world
· one point of elevation from each continent
· at least five of the places you choose must have an elevation below sea level (0 m)

*Make sure you record only elevations that are measured in metres (m).
Create a table that includes the names of your 10 points and their elevations.
Choose two locations from your table to be your mystery elevations. Make up a set of five operations for each mystery elevation that will lead your partner to the correct integer (elevation). Double check to make sure that all of your operations are correct.
Your operations must include:
· the addition of a negative integer
· the subtraction of a negative integer
Exchange your table and your set of five operations for each mystery elevation with a partner. Have him or her complete the operations to find your two mystery elevations. Hint: one way you can check if you likely have the right elevation is to make sure the answers (elevations) you come up with appear on your partner’s table.

RESOURCES

Websites:

Nation Master - Lowest Elevations

Nation Master - Highest Elevations

World Land Areas and Elevations

Exxun - Elevation Extremes
Statistics Canada

Materials:

Paper, pencil, and ruler (to create a table for all 10 elevations)
Calculator (optional)
Number line (optional)

ASSESSMENT

	Level 1	Level 2	Level 3	Level 4
Understanding Concepts (Elevation and Integers)	I have a basic understanding of the concept of elevation as height above or below sea level. My operations for the mystery elevations contain errors, do not include the addition of a positive integer and the subtraction of a negative integer, and are very easy.	I have some understanding of the concept of elevation as height above or below sea level. Myoperations for the mystery elevations are all or mostly correct, but may not include the addition of a positive integer and the subtraction of a negative integer, and/or are of below average difficulty.	I have an accurate understanding of the concept of elevation as height above or below sea level. My operations for the mystery elevations are correct, include the addition of a positive integer and the subtraction of a negative integer, and are of average difficulty.	I have a complete an accurate understanding of the concept of elevation as height above or below sea level. Myoperations for the mystery elevations are correct, include the addition of a positive integer and the subtraction of a negative integer, and are more difficult than average.




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