1. Using Mental Math to Multiply – Breaking Apart Method
Lesson 5.2
Using Mental Math to Multiply – Breaking Apart Method

2. Review
4 x 30 =
6 x 400 =
300 x 9 =
50 x 7 =

3. Set the Purpose
You learned how to multiply multiples of Today, you will learn other strategies to help you multiply mentally.
Connect – What are some examples of times you might want to multiply mentally?

4. Pose the Problem
Suppose you ride your bicycle 27 kilometers each week. What multiplication sentence can you write to show the number of miles you ride in 3 weeks?
How can you multiply mentally?

5. Whole-Class Discussion
3 x 27
27 =
So, 3 x 20 = 60
and 3 x 7 = 21.
So,
= 81

6. Mental Math to Multiply
Abdulla rode his bike for 18 kilometers each day for 3 days. How many kilometers did he ride his bike in all?
Find 3 x 18 mentally.
Break apart 18 into 10 and 8.
Think of 3 x 18 as
(3 x 10) + (3 x 8).

7. Together! 3 x 34: Breaking apart: (3 x ____) + (3 x ____) =
Break Apart!
3 x 34: Breaking apart: (3 x ____) + (3 x ____) =
8 x 14: Breaking apart: (8 x _____) + (8 x _____) =
7 x 22: Breaking apart: (7 x ______) + (7 x _____) =

8. On your own!
Break Apart!
5 x 64: Breaking apart: (5 x ____) + (5 x ____) =
2 x 18: Breaking apart: (2 x _____) + (2 x _____) =
3 x 37: Breaking apart: (3 x ______) + (3 x _____) =

9. Try on your own – BREAK APART!
8 x 44 =
9 x 13 =
51 x 6 =
17 x 4 =

10. Homework
Pg. 98 (#7-20)
DO NOT DO # 9 and # 10

11. Extra Problems

12. Extra Problems

13. Extra Problems