February 17, 2009 New tables today! One person may stay at their table; the rest must move. Sit with three new people.

February 17, 2009 Multiplication Models (section 3.3) Begin Exploration 3.13 Homework (need Class Notes) *Bring Class Notes on Thursday, 2/19.

3.3 – Understanding Multiplication Meanings for multiplication: 1.Repeated addition Ex: One piece of candy costs 4 ¢. How much would 3 pieces cost? 3·4 = = 12 (note that 4 ·3 = = 12 = 3·4)

2. Measured units Ex: If James has 3 pieces of fence that are each 4 feet long, how many feet of fence does he have, total? 3.3 (cont’d)

3. Area Ex: A poster measures 3 feet by 4 feet. What is the area of the poster? Notice that this amounts to adding up units of a new measure! 3.3 (cont’d) 4 ft 3 ft

4. Cartesian Product Ex: Stacy has packed 4 shirts and 3 pairs of pants. How many combinations can she wear? 3.3 (cont’d) Shirt 1Shirt 2Shirt 3Shirt 4 P1 P2 P3

5. Arrays Ex: A classroom has desks in 3 columns and 4 rows. How many students can be seated? 3.3 (cont’d)

Can you think of other meanings for multiplication? 3.3 (cont’d)

General model for multiplication: n is called the multiplier, a is called the multiplicand, and b is called the product. We also say n and a are factors of b, and that b is a multiple of both n and a.

Exploration 3.13 Read the Egyptian Duplation example (focus on the Hindu-Arabic numerals). Working with a partner, explain what is going on here and why it works. Try using this method to compute 14 · 41, 65 · 17, and 18 · 37

Homework Due Thursday, 2/19: Link to online homework list