How do you spot a multipe of eight?

Question

There are ways to spot different multiples

for example 81 is a multiple of 9 and if you add the digits (8+1) it makes nine.

How do you spot a multiple of eight?

Answer 1

The rule for 8 is that the last three digits are a multiple of eight.

So if you had 143,128 then you need to check the last 3 digits: 128.

A way to quickly check those 3 digits is to divide by 2. If you can do it three times, it is a multiple of 8.

128 / 2 = 64
64 / 2 = 32
32 / 2 = 16

So 143,128 is a multiple of 8.

Answer 2

If the last 3 digits of a number a divisible by 8 the entire number is divisible by 8.

Penelope...The rule is if the digits add up to a multiple of 9 then it works. 18 is a multiple of 9. Also if you keep adding up the digits until you get to a single digit you'll get 9. Using your example 297 add them up get 18 add them up get 9.

The other rules are this:

2 - Any even number (number ending in 0, 2, 4, 6, 8)
3 - When the sum of the digits equal to a multiple of 3. (You can keep adding until you get to a single digit. Using the previous example 297...sum is 18, sum is 9 you know 9 is a multiple of 3, as is 18)
4 - If the last two digits of a number are divisible by 4 the entire number is divisible by 4
5 - Any number ending in 5 or 0
6 - If a number is divisible by 2 AND 3 it is divisible by 6
7 - I don't know of a rule for 7
8 - If the last 3 digits of a number is divisible by 8 the entire number is divisible by 8
9 - If the sum of the digits add up to a multiple of 9, the number is divisible by 9. (You can keep adding until you get to a single digit. Using the previous example 297...sum is 18, sum is 9 you know 9 is a multiple of 9, as is 18)
10 - Any number ending in 0

Hope that helps you guys...Good Luck

Answer 3

Check the last three digits, and see if they have 8 as a divisor.

But if you're as lazy as me, you'll do it differently: if the hundred's place is even, check to see the last two digits are in your eight-times-table, including up to twelve. If the hundred's is odd, check to see if four less than the last two digits is divisible by eight.

For example: 672 is, because 6 is even, so we check the 72; sure enough, 72 = 8x9.

544 is, because, noticing that the 5 is odd, we check 44-4, or 40, and 40 = 8x5.

468 is not, because, since 4 is even, we check 68, which is not 8 times anything from 1 to 12.

540 is not, because, since 5 is odd, we check 40-4, or 36, which is not in the eight tables.

911 is not, because it's odd. That one was easy!

Answer 4

It divides by eight exactly!
As for the first answerer, Your answer is slightly flawed because you give the answer as 18 and 1+8 = 9.
that works nicely.

For the 9 times table - try holding out both hands, fingers extended.
Bend in the one on the far left, this makes 9
then fold in the adjacent finger and re-extend the furthest left.
Count the furthest left as a 10 and the others as units - it makes 18.
Continue along with the next finger in the same way as before.
it follows the pattern - 9-18-27-36-45-54-63-72-81-90,
Cool way to remember but i dont think there's a way to do 8's.

Answer 5

about what penelope siad: that 9 rule doesn't always work (297 is a multiple of 9 and it's digits add up to 18)

it does work see you add the digits 2 + 9 +7 and you get 18 BUT 1+8=9

so it works

Answer 6

There is no special way to identify a number as a multiple of 8, but if you can identify it as a multiple of 4, you have a 50/50 chance it's a multiple of 8. Numbers are multiples of 4 is the last 2 digits are divisible by 4, like 1348. After dividing by 4, if you get an even number, it's a multiple of 8. Otherwise, if you get an odd number, it's only a multiple of 4.

Answer 7

297 is a multiple of 9 and they do add up to 18 but 1 and 8 = 9

Answer 8

Each ends in 8, 6, 4, 2, 0, as you go along the sequence. Example:- 8, 16, 24, 32, 40, 48, 56, 64, 72, 80.

Answer 9

you divide it by eight and see if there's any decimals
plus, that 9 rule doesn't always work (297 is a multiple of 9 and it's digits add up to 18)

Answer 10

I dont know exactly but I dont think you can spot any using that method