Preliminaries
Whole Numbers
The following set of rules can help you save time in trying to check the divisibility of numbers. Instead of actually dividing into the numbers, try the rules in Table 1.
|
A number is divisible by |
if |
|---|---|
|
2 |
it ends in 0,2,4,6, or 8 |
|
3 |
the sum of its digits is divisible by 3 |
|
4 |
the number formed by the last two digits is divisible by 4 |
|
5 |
it ends in 0 or 5 |
|
6 |
it is divisible by 2 and 3 (use the rules for both) |
|
7 |
(no simple rule) |
|
8 |
the number formed by the last three digits is divisible by 8 |
|
9 |
the sum of its digits is divisible by 9 |
Example 1
Answer the following.
.
Is 126 divisible by 3?
.
Is 1,648 divisible by 4?
.
Is 186 divisible by 6?
.
Is 2,488 divisible by 8?
.
Is 2,853 divisible by 9?
.
4,620 is divisible by which of the following numbers?
2, 3, 4, 5, 6, 7, 8, 9.
