Page 199 - NUMINO TG_3A

Activity 2

4. Have students solve the following problems 4 . Multiply 3 numbers. Find the fastest way to multiply.
using the properties of multiplication.
START 3 120 73
Have students, who were able to solve the 85 2
problem before others, present to the class
how he or she solved the problem. 42
How to calculate the three numbers quickly:
56 7 5
3, 8, 5 8 5 3 40 3 120 4 9
7, 3, 2 2 3 7 6 7 42 3
5, 9, 4 5 4 9 20 9 180 93 2 4
7, 4, 2 4 2 7 8 7 56
3, 9, 3 3 3 9 9 9 81 81 7 180
5, 9, 6 6 5 9 30 9 270 12
12, 7, 5 12 5 7 60 7 420 FINISH
8, 5, 16 16 5 8 80 8 640 5
640
59
6 8
16
270
5
114
420

Multiplying Three Numbers

You can multiply three numbers quickly if you calculate them in the following ways.

Change the numbers into ones: Change the numbers into tens and ones:

(1-digit number) (1-digit number) Tens (1-digit number)

Example: 7, 3, 2 ( 2 3 ) 7 6 7 42 Example: 3, 8, 5 (8 5) 3 40 3 120

7, 4, 2 ( 4 2 ) 7 8 7 56 5, 9, 4 (5 4) 9 20 9 180

3, 9, 3 ( 3 3 ) 9 9 9 81 5, 9, 6 (6 5) 9 30 9 270

12, 7, 5 (12 5) 7 60 7 420

8, 5, 16 (16 5) 8 80 8 640

182 NUMINO Teacher s Guide