secrets-of-mental-math-malestrom

Products of a Misspent Youth: Basic Multiplication 35
its because the subtraction portion of the problem gets difficult.
As it is, you may prefer to stick with the addition method. Personally,
for problems of this size, I use only the addition method
because in the time spent deciding which method to use, I could
have already done the calculation!
So that you can perfect your technique, I strongly recommend
practicing more 2-by-1 multiplication problems. Below are
twenty problems for you to tackle. I have supplied you with the
answers in the back, including a breakdown of each component
of the multiplication. If, after you’ve worked out these problems,
you would like to practice more, make up your own. Calculate
mentally, then check your answer with a calculator. Once
you feel confident that you can perform these problems rapidly
in your head, you are ready to move to the next level of mental
calculation.
EXERCISE: 2-BY-1 MULTIPLICATION
82
9
43
7
67
5
71
3
1. 2. 3. 4. 5.
93
8
49
9
28
4
53
5
84
5
6. 7. 8. 9. 10.
58
6
97
4
78
2
96
9
75
4
11. 12. 13. 14. 15.
57
7
37
6
46
2
76
8
29
3
16. 17. 18. 19. 20. 64
8