Math Focus 5
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Counting Caribou

INTRODUCTION

Twice a year, caribou go on a long trek. In the spring they head north onto the tundra, where their calves are born, and in the fall the adults and the calves head south toward the forest. When they move, they travel in big herds. But just how big is each herd? Is the herd growing or shrinking? Wildlife managers need to know.

You will estimate the size of a herd of caribou.

THE PROCESS

1. Look on the web for an aerial photo of a herd of caribou, like this National Geographic photo, or this image at Corbis. Try to choose a photo with LOTS of caribou.
2. Print the image.
3. Draw a grid over the photo.
4. Pick one square in the grid that contains caribou. How many caribou can you count in the square?
5. How many squares contain caribou?
6. Multiply the number of caribou in the square by the number of squares. About how many caribou are in the photo?
7. Is your estimate high or low? Explain how you know.
8. Could you make a better estimate by changing the size of your grid or by choosing a different first square? Explain.
9. What is your best estimate of the number of caribou in the photo?

Websites:

Corbis

Materials:

printer
pencil
ruler

ASSESSMENT

 Criteria Work meets standard of excellence Work meets standard of proficiency Work meets acceptable standard Work does not yet meet acceptable standard Mental Mathematics and Estimation: Estimates possible solutions Chooses an efficient and effective strategy to estimate a solution. Chooses a workable and reasonable strategy to estimate a solution. Chooses a familiar strategy to estimate a solution. Chooses a random or inappropriate strategy to estimate a solution. Reasoning: Makes generalizations Comprehensively analyzes situations and makes insightful generalizations. Completely analyzes situations and makes logical generalizations. Superficially analyzes situations and makes simple generalizations.. Is unable to analyze situations and make generalizations.. Communication: Explains mathematical procedures Provides a precise and insightful explanation of a procedure. Provides a clear and logical explanation of a procedure. Provides a partially clear explanation of a procedure. Provides a vague and/or inaccurate explanation of a procedure.