Multiplication Review: Part 1
A. Vocabulary
Factors are the numbers you multiply.
The product is the answer you get when you multiply.
Ex. 9 X 7 = 63
9 and 7 are the factors. 63 is the product.
B. Strategies to help you multiply
(until you have the facts memorized)
1. Use doubling to multiply by 4.
2 x 7 = 14 so… 4 x 7 = 14 + 14 = 28.
If you double one of the factors, the product doubles.
2. Use repeated doubling to multiply by 8.
2 x 8 = 16
4 x 8 is double 2 x 8 so 4 x 8 = 16 + 16 = 32
8 x 8 is double 4 x 8 so 8 x 8 = 32 + 32 = 64
3. Begin with a fact you know and double one of the factors.
If you know 3 x 4 = 12 but you don’t know 6 x 4, you can double 12 and get the answer.
3 x 4 = 12
6 is 3 doubled, so 6 x 4 = 12 + 12 = 24
That means 3 x 8 = 24 too because when you double 4 you get 8.
4. Start with a fact you know and add on a group.
If 2 x 7 = 14, then 3 x 7 = 14 + one group of 7
So, 3 x 7 = 14 + 7 = 21
5. Use facts with 5 and 2 to multiply by 7.
Think: 5 x 8 = 40
2 x 8 = 16
So
7 x 8 = 40 + 16 = 56
6. Use facts with 10 to multiply by 9.
To find 9 x 6, think: 10 x 6 = 60
So, 9 x 6 = 60 minus one group of 6.
9 x 6 = 60 – 9 = 54
*You can also use the finger trick!
Practice *Remember- the goal is to memorize these facts. Use the strategies until you have
them memorized.
1.
2.
3.
4.
5.
6.
2x9=
3x9=
4x9=
8x9=
5x6=
6x6=
7. 4 x 6 =
8. 8 x 6 =
9. 6 x 9 =
10. 10 x 6 =
11. 7 x 7 =
12. 3 x 8 =
13. 4 x 1 =
14. 8 x 8 =
15. 6 x 3 =
16. 2 x 7 =
17. 8 x 0 =
18. 7 x 8 =
19. 9 x 7 =
20. 6 x 5 =
Problems *Remember to show your work!
1. Lea knows the product of 8 and 9 is 72.
How can she use that fact to find the product of 7 and 9?
2. How can you use 7 x 10 to find 9 x 7?
3. How can you find 6 x 7 if you know 6 x 6?
4. Susan knows the product of 2 and 4. How can she use that product to find 4 x 4?
5. How can Susan use the product of 2 x 4 to find 8 x 4?
6. How can you find the product of 9 x 7 if you know the product of 9 x 5?