Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

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?

 Session 5: Index | Notes | Solutions | Video