Post by Admin on Oct 2, 2021 6:44:34 GMT 7
To see whether a number is divisible by 3, we simply find the sum of its digits. If the sum is a multiple of 3, then the number is indeed divisible by 3.
Examples:
8 + 7 = 15
15 is a multiple of 3, so 87 and 78 are both divisible by 3.
4 + 3 = 7
Therefore, neither 43 nor 34 is divisible by 3.
2 + 2 + 2 = 6
222 is divisible by 3.
2 + 3 + 4 = 9
234 is divisible by 3. So are 243, 324, 342, 423 are 432.
5 + 7 + 7 = 19
577, 757 and 775 are all not divisible by 3.
The rule can be applied to any number, no matter how many digits it has. If the sum arrived at is too big for you to calculate mentally, you can apply the rule to that sum again.
Example:
9 + 9 + 8 + 8 + 8 + 8 + 7 + 7 + 7 + 7 = 78
7 + 8 = 15
9,988,887,777 is divisible by 3. In fact, any number with this combination of digits is divisible by 3. Such as 8,877,998,877, 8,877,998,877, 8,877,998,877. That's because they all have the same sum, 78.
Examples:
8 + 7 = 15
15 is a multiple of 3, so 87 and 78 are both divisible by 3.
4 + 3 = 7
Therefore, neither 43 nor 34 is divisible by 3.
2 + 2 + 2 = 6
222 is divisible by 3.
2 + 3 + 4 = 9
234 is divisible by 3. So are 243, 324, 342, 423 are 432.
5 + 7 + 7 = 19
577, 757 and 775 are all not divisible by 3.
The rule can be applied to any number, no matter how many digits it has. If the sum arrived at is too big for you to calculate mentally, you can apply the rule to that sum again.
Example:
9 + 9 + 8 + 8 + 8 + 8 + 7 + 7 + 7 + 7 = 78
7 + 8 = 15
9,988,887,777 is divisible by 3. In fact, any number with this combination of digits is divisible by 3. Such as 8,877,998,877, 8,877,998,877, 8,877,998,877. That's because they all have the same sum, 78.