# Write a divisibility rule for 12

Is 5 divisible by 1? Therefore it is divisible by 2. If the last three digits of a whole number are divisible by 8, then the entire number is divisible by 8.

Here, you are divisible by 5 but not by 2. So this also is not divisible by 9. So, if we can show that 3, 6 or 9 go into the number, we know that the number is not prime without doing any long division. So it's clearly divisible by 20, and if you were to divide it by 12, you'd divide it by 2 times 2 times 3.

And we already have at least one 3 from the 9, so we have that. Now, the number 6. Prime factorization of 24 is 2 times The Rule for 3: Does 8 divide evenly into ?

So 4 plus 8 is equal to 12, and 12 clearly is divisible by 3. So 3 is a factor of 34, And this is the easiest one of all, because you just have to see if you have a 0 in the ones place. So 3 is not a factor of 45, Well, we already summed up the digits here, Now check whether the sum is divisible by 3 or not. So the digits add up to 9. It is divisible by 4. Divisibility Rules By Education Free 3 Comments Here is an easy way to learn weather a given number is divisible by another.

The Rule for 3: Basically, we will see if the sum of the digits is divisible by 9. So we can use a very similar rule to determine if a number is divisible by 9. Factors Prime numbers Multiples Video transcript - [Voiceover] In this video I wanna do a bunch of example problems that show up on standardized exams and definitely will help you with our divisibility module because it's asking you questions like this.

If that sum is divisible by 9, then you're there. So we've gone through the 2s. What does this mean? Do this sequence until only 2 digits remain and those 2 digits should be divisible by So to test whether any of these are divisible by 2, you really just have to look at the ones place and see if the ones place is divisible by 2.

Proofs Now, we will be discussing the derivations of these rules. Sum up all the digits. So this number is not divisible by 8 The rules for 2, 4, and 8 should all look similar. Dividing it by 20 is the same thing as dividing by 2 times 2 times 5, so you're going to have the 2's are going to cancel out, the 5's are going to cancel out.

And actually I just realized that this is a silly answer because obviously all numbers divisible by 9 and 24 are also divisible by 9. YES 2 Divisibility rule for number 2: Now, let's work through the 3s. This means that the number is EVEN and 2 will divide into it without a remainder.

So this one's not divisible by any of the first few numbers right over here. We know that 2 times 3 times 5 is divisible into it. So this number is not divisible by 8 The rules for 2, 4, and 8 should all look similar.

There is a divisibility rule for every number. Divisibility Rules Divisibility Rules Mathematics is not very easy for some of us.

So I won't write any 2 there. These are the only numbers that we can assume are in the prime factorization of something divisible by both 9 and Since 6 is a multiple of 2 and 3, the rules for divisibility by 6 are a combination of the rule for 2 and the rule for 3.

In other words, a number passes this divisibility test only if.  