1. Multiplying with 8 and the Associative Property of Multiplication MAFS.3.OA.3.7 MAFS.3.OA.2.5

2. Lesson Opening Solve the two problems below. Write the equation you used to solve the problem. 1.If 27 apples are to be packed in boxes of 9, how many boxes are needed? 2.For a project, Sue needs 6 pieces of string that are each 4 yards long. If Sue has 20 yards, will she have enough string?

3. Lesson Opening Solve the two problems below. Write the equation you used to solve the problem. 1.If 27 apples are to be packed in boxes of 9, how many boxes are needed? 2.For a project, Sue needs 6 pieces of string that are each 4 yards long. If Sue has 20 yards, will she have enough string? 27 apples in boxes with 9 in each box 27 ÷ 9 = 3 or 9 x ____ = 27 Three boxes are needed. 6 pieces of string that are 4 yards each 6 x 4 = 24 Is 20 yards enough? NO! She will not have enough string. She will need 4 more yards.

4. The Associative Property of Multiplication Each car on the roller coaster has 2 rows of seats. Each row has 2 seats. There are 3 cars in each train. How many seats are on the train?

5. The Associative Property of Multiplication Each car on the roller coaster has 2 rows of seats. Each row has 2 seats. There are 3 cars in each train. How many seats are on the train?

6. The Associative Property of Multiplication Each car on the roller coaster has 2 rows of seats. Each row has 2 seats. There are 3 cars in each train. How many seats are on the train?

7. The Associative Property of Multiplication Each car on the roller coaster has 2 rows of seats. Each row has 2 seats. There are 3 cars in each train. How many seats are on the train? (2 X 2) x 3

8. The Associative Property of Multiplication Each car on the roller coaster has 2 rows of seats. Each row has 2 seats. There are 3 cars in each train. How many seats are on the train? (2 X 2) x 3 becomes 2 x (2 x 3)

9. The Associative Property of Multiplication Each car on the roller coaster has 2 rows of seats. Each row has 2 seats. There are 3 cars in each train. How many seats are on the train? (2 X 2) x 3 becomes 2 x (2 x 3)

10. The Associative Property of Multiplication This property, like all properties of operations, are meant to help us. 8 x 7 42 x x7() 4 2 x ()x 7 282 x = 56

11. Multiplying with 8 Write your 2s facts from 0 to 10: 0 × 2 = 1 × 2 = 2 × 2 = 3 × 2 = 10 × 2 =

12. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6

13. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Whoa, that’s a lot of smiley faces to count!

14. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Whoa, that’s a lot of smiley faces to count! I know that 4 x 6 is 24, then I can double 24.

15. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Whoa, that’s a lot of smiley faces to count! I know that 4 x 6 is 24, then I can double 24. 24 doubled is 48. So, 8 x 6 = 48

16. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Whoa, that’s a lot of smiley faces to count! What if you didn’t know what 4 x 6 was?

17. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Whoa, that’s a lot of smiley faces to count! What if you didn’t know what 4 x 6 was? You could multiply 2 x 6!

18. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Whoa, that’s a lot of smiley faces to count! What if you didn’t know what 4 x 6 was? You could multiply 2 x 6 which is 12.

19. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Whoa, that’s a lot of smiley faces to count! What if you didn’t know what 4 x 6 was? You could multiply 2 x 6 which is 12. Then you could double 12, which is 24.

20. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Whoa, that’s a lot of smiley faces to count! What if you didn’t know what 4 x 6 was? You could multiply 2 x 6 which is 12. Then you could double 12, which is 24. Then you could double 24, which is 48.

21. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 You are using the Distributive Property or the Associative Property when you are doubling your 4 fact to give you your 8 fact.

22. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Distributive Property (4 x 6) + (4 x 6) = 48

23. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Associative Property 2 x (4 x 6) = 48 or (2 x 4) x 6 = 48 Since there are 2 groups of 4 x 6

24. Multiplying with 8 Doubling your 4 fact is a strategy you can use for multiplying by 8. 8 x 6 Associative Property 2 x (4 x 6) = 48 or (2 x 4) x 6 = 48 Since there are 2 groups of 4 x 6 2 x 4 = 8

25. Multiplying with 8 So, what is… 8 groups of 3 (8 x 3) 8 groups of 6 (8 x 6) 8 groups of 8 (8 x 8) 8 groups of 7 (8 x 7) 8 groups of 9 (8 x 9) Think: 2 × 3 = 6, now double 6, now double that… Think: 2 × 6 = 12, now double 12, now double that… Think: 2 × 8 = 16, now double 16, now double that… Think: 2 × 7 = 14, now double 14, now double that… Think: 2 × 9 = 18, now double 18, now double that…

26. Multiplying with 8 Another strategy is to use the Distributive Property with facts you know. 8 x 6

27. Multiplying with 8 Another strategy is to use the Distributive Property with facts you know. 8 x 6 I know 5 x 6, which is 30. (5 x 6)

28. Multiplying with 8 Another strategy is to use the Distributive Property with facts you know. 8 x 6 I know 5 x 6, which is 30. What’s left is 3 x 6, which I also know. 3 x 6 is 18. (5 x 6) + (3 x 6)

29. Multiplying with 8 Another strategy is to use the Distributive Property with facts you know. 8 x 6 30 + 18 = 48 (5 x 6) + (3 x 6) = 48

30. Multiplying with 8 Another strategy is to use the Distributive Property with facts you know. 8 x 6 30 + 18 = 48 (5 x 6) + (3 x 6) = 48 = 48

31. Multiplying with 8 Let’s look at our Multiplication Table…

32. Multiplying with 8 Find all the multiples of 8… The ones place has a pattern of 6, 4, 2, 0, 8… All the multiples are even numbers

33. Multiplying with 8 Let’s look at our 100 Chart…

34. Multiplying with 8 Look at the multiples of 8… A diagonal pattern is formed, going to the right, because the multiples are each less than 10. All the multiples are even numbers.

35. Playing with Doubles You need: a set of cards (0-10) Playing with Doubles sheet Directions: Flip over a card and write that number in the first column Double the number (write that in the second column) Double that number (write that in the third column) Double that number (write that in the fourth column) Look for patterns in your products Answer the questions on the back

36. Crazy Eight You need: a set of number cards (0-10) Crazy Eight game board Directions: The first player flips over a number card and multiplies it by 8. Then, the player covers the product on their game board If the product is already covered you lose that turn. The second player repeats the above steps. The first player to cover the entire board is the winner.

37. Closing What is one strategy you used for multiplying with 8? Double the 2 fact TWICE (For 8 × 7: 2 x 7 = 14, double 14 = 28, double 28 = 56.) Double the 4 fact (For 8 x 7: 4 x 7 = 28, then double 28 = 56 This is really using the Associative Property: 2 x (4 x 7) Use the Distributive Property 8 x 7 = (5 x 7) + (3 x 7) = 56

38. Bonus Question When you multiply any number by 8, is the product… a)always odd? b)always even? c)sometimes even, sometimes odd? d)neither even nor odd? How do you know?

39. Exit Ticket 1.Octopus have 8 legs. How many legs do 9 octopus have? a.Model the problem. b.Write an equation that corresponds to it. c.Write another equation that corresponds to it. d.Write the answer to the problem in a complete sentence. 2.Show another way to group the multiplication expression below, then solve. (2 x 4) x 9