What multiply by 12?

Answer 1

Everything multiplies by 12.

Do you mean how do you figure out what is divisible by twelve just by looking at it?

If so, it needs to be both divisible by 3 and 4.

A test for divisibility by 3 is to add up all the digits in the number. If the result is divisible by 3 then the number is divisible by 3.

For example. 12 is divisible by three. as 1+2=3 which is divisible

411 is also divisible by three. as 4+1+1=6 which is divisible by 3.

(if you end up with a double digit as your answer, do the same method again)

To determine whether something is divisible by four, take the last two digits. If 4 divides these two digits then four divides your number.

for example. 912316 -> 16 is divisible by 4. therefore 4 divides 912316.

Now, to find if a number is divisible by 12. we need to satisfy both of these requisites.

lets take the above number again.

912316 is divisible by 4 as we already proved.

now, to be divisible by 12 we need to see if three divides it.

9+1+2+3+1+6 = 22 = 2+2 = 4 which is not divisible by 3. therefore 912316 isn't divisible by 12.

but lets take another number...

114768

does 4 divide 68? well we can subtract 40 as we know that 4 divides 40 ten times.

does four divide 28? yes. it does. 7 times.

test for 3

1+1+4+7+6+8 = 27

do the same again.

2+7 = 9

3 divides 9.

therefore 12 divides 114768!!

Hope this clears it up for you!!