Wednesday, May 6, 2009

Rules of Divisibility

An integer is
divisible by...

If...

Example

2

its last digit is even

210 is even and so is divisible by 2

3

its digits add up to a multiple of 3

18,255: add up the digits: 1+ 8 + 2 + 5 + 5 = 21 and 21 is a multiple of 3

4

its last 2 digits are a multiple of 4

59,456: 56 ÷ 4 = 14, so 56 is a multiple of 4, which makes 59,456 divisible by 4

5

its last digit is 0 or 5

34,875 6,730

6

it's a multiple of 2 and 3

558 is even and so is a multiple of 2, and adding the digits gives: 5+5+8=18, and 18 is a multiple of 3, so 558 is divisible by 6

8

its last 3 digits are a multiple of 8

6,417: add the digits: 6+4+1+7=18, and 18 is a multiple of 9

9

its digits add up to a multiple of 9

17,336: 336 ÷ 8 = 42, so the last 3 digits are a multiple of 8, which makes 17,336, div.ble by 8

10

it ends in 0

93,674,280

12

it's a multiple of 3 and 4

4,932: 4+9+3+2=18 which is a multiple of 3, and 32 ÷ 4 = 8, so the last two digits are a multiple of 4

0 Comments:

 

Interview Preparation | Placement Papers