Prime Numbers

Prime numbers are numbers with only two factors. This basically means numbers which you will only find in the 1 times table of their own times table. For example, 5 is prime because it is only in the 5- and 1-times table, where are 10 is in the 1, 2, 5, 10 times tables so it wouldn’t be prime.

If you are practicing the prime numbers (I’ll put a 100 number grid in the 11+ resources today) create a visual table to help you to solve them quickly until you gain confidence.

Start by colouring square number 1. This is not prime as it is only in the 1x table and no other (so it has 1 factor instead of the necessary 2).

Now colour in everything in the 2x tables apart from 2. So, colour in the column below the 2 (but not the 2), the column where every number ends in 4. The 6 column, the 8 column, and the 10’s column. (2 is the only even prime number)

Next, we’ll colour in everything in the 5’s column APART from number 5.

Now we need to colour in all the multiples of 3 apart from 3. The easiest ways to do this is just colour in the ones you know which are multiples of 3 or to count on 3. However, if you’re not sure any number where the digits add together to create a number that is in the 3x table, it will be a multiple of 3.

Example: 96

9+6=15 (in the 3 times table but just to be sure add the digits in 15 together)

1+5 =6, also in the 3x table.

However, 43

4+3 =7

7 isn’t in the 3x table so neither is 43.

We completed the 4’s when we coloured in the 2’s so we don’t need to worry about that, and the 5’s were also completed. 

The 6’s were completed when we coloured in the 3’s so that’s done, so now we need to do the 7’s.

Unfortunately, there are no tricks for this one. It will be a case of just colouring in the ones you know and counting on for the ones in between. However, fortunately there won’t be many to do.

We’ve done the 8’s when we completed the 2’s or 4’.

The 9’s were done with the 3’s.

The 10’s were completed with the 5’s.

If there are any in the 11x table left, feel free to colour this in.

The 12’s were done with the 2’s, 3’s, 4’s, 6’s, 

What’s left not coloured in, are the prime numbers. You might choose to make those numbers into something more visually appealing or you may just look at those sheets for guidance, the choice is yours.

I don’t know if I’ve mentioned this game before. I used to play it a lot as a child when we went to a friend’s house so impart, I think I associate it with childhood memories and them.

Anyway, what I have done is taken out all the faces and swapped them with numbers. The numbers include prime numbers, even numbers, square numbers, odd numbers, numbers in the 3x table, numbers in the 5x table, etc. up to 100.

Now instead of trying to guess the person the other person has; you must guess the number by asking a series of questions. “Is it odd?” “Is it a 2-digit number?" etc. If I say it’s odd, they need to put down all the even numbers. In theory the number left standing at the end is the number the other person has.

It’s good fun, and an enjoyable way of practicing number values such as odd, even, prime, square, multiples, etc depending on the stage your child is at.