#### Alison Kimbley

pdf

Subject Area:

Mathematics

Strand:

Number

Four

Content (topic)

Understanding Addition and Subtraction of Decimals

WNCP:

 Outcome N4.8: Demonstrate an understanding of addition and subtraction of decimals limited to hundredths (concretely, pictorially, and symbolically) by: Using compatible numbers Estimating sums and differences Using mental math strategies solving problems. Indicators: Approximate sums and differences of decimals using estimation strategies. Solve problems, including money problems, which involve addition and subtraction of decimals, limited to hundredths. Count back change for a purchase. Explain the strategies used to determine a sum or difference. Mathematical Processes: Mental Mathematics and Estimation Communication Problem solving Reasoning Visualization

Lesson Preparation:

Equipment/materials:

• Index cards which have the beaver pelts as well as the trade goods.
• Show the class a picture of Thanadelthur.

• Prepare index cards with pictures of fur bearing animals that represent the pelts as well as the trade items.
• Arrange the room appropriately that will allow space for the different groups.
• Print a copy of Appendix A for each trading post.

Presentation:

Set

Development

• Have the students explore the fur trade charts (Appendix A) in order to determine how many furs were needed for products.

• Have the students discover mathematical patterns by role-playing a trading post.

• Tell the students that they will be trading items once traded by Aboriginal people (such as the Denesuline people) and the Europeans. Half the class will serve as the Aboriginal traders and draw a variety of fur bearing animals, such as the beaver, lynx, otter, raccoons and coyotes, whereas the other half of the class will need to draw pictures of items brought from Europe such as blankets, axes, knives, coils of rope, beads, etc.

• Find places in the room where small groups can start up trading posts. Explain to the class that trading posts were where fur traders typically displayed their goods. Students will take turns being the clerk who usually worked for the Hudson Bay Company. Have the Aboriginal role-players take turns bringing the furs to the clerk. It was the clerk who normally handles the trades for the HBC and the clerk would use multiplication in order to determine the exchange.

• The students playing the part of the Aboriginal people in the fur trade will take turns bringing the furs to trade at the trading post. They and the traders should refer to the posted “Value of Furs” and “Value of Trade Goods” chart to determine the number of required furs.

• Before the students start this activity, provide them with an example of role-play. For example at one of the designated stations, approach the students with a number of pelts and ask for a certain trade item. Estimate how many more pelts you would need to equal the correct amount for the trade item. The clerk will need to solve this problem by finding out the exact amount of pelts needed. After the clerk has determined the amount, the European trader (the student who the trade item belonged to) will then count back change from the purchase. The person who had traded must explain the strategies used to determine a sum of difference in the numbers.

• It is important the students understand that in the fur trade, the HBC clerks ensured that the numbers were exact and therefore did not estimate the sums. However, in this exercise they will be estimating prior to solving each problem.

Appendix A:

The text below is adapted from the Albany Fort America Journal of 1706. Fort Albany was a fur-trading post in northern Ontario, at the mouth of the Albany River on James Bay. It was founded (before 1682) by the Hudson's Bay Company as one of its earliest forts.

Value of Furs

1 Beaver = 2 Lynx = 2 Land Otters = 3 Raccoons = 4 Coyote