Session 5, Part B: Divisibility Test (50 minutes)
In This Part: Developing Testing Rules | Divisibility Tests for 2, 5, and 10 Divisibility Tests for 3 and 9 | Divisibility Tests for 4 and 8 | Divisibility Test for 11
Another way to examine the characteristics of base ten numbers is to look at the patterns that emerge when we try to determine whether a particular number is evenly divisible by another number. Note 2
Use the following numbers for Problems B1 and B2. Remember, we are only looking for patterns here. The actual divisibility rules will be explored in the following sections.
Row
Numbers
1
1
11
21
31
151
2461
2
2
12
22
32
152
2462
3
3
13
23
33
153
2463
4
4
14
24
34
154
2464
5
5
15
25
35
155
2465
6
6
16
26
36
156
2466
7
7
17
27
37
157
2467
8
8
18
28
38
158
2468
9
9
19
29
39
159
2469
10
10
20
30
40
160
2470
Problem B1
a.
Which of the above numbers are divisible by 2?
Look across the rows of numbers. Do you see any patterns?
Close Tip Look across the rows of numbers. Do you see any patterns?
b.
Which of the above numbers are divisible by 5?
c.
Which of the above numbers are divisible by 10?
d.
What is the test for divisibility by 2, 5, or 10?
Which digits of the number must you examine to test for divisibility by 2, 5, or 10? Why?
Close Tip Which digits of the number must you examine to test for divisibility by 2, 5, or 10? Why?
Problem B2
a.
Which of the above numbers are divisible by 9?
Look across the rows or columns of numbers. Do you see any patterns?
Close Tip Look across the rows or columns of numbers. Do you see any patterns?
b.
Which of the above numbers are divisible by 3?
c.
What is the test for divisibility by 9 or 3?
