# Build the 7s

As you start to get more familiar with the colours and the cards you might be ready to create a new set!

You'll notice that 7 is not part of the pack and neither is 14 or other numbers in the 7 times table. This is because you need 7 to make these numbers. 7 is known as a prime number (just like the other numbers that have 1 disk on them)

## Quick Start

## Set Up

### Set up

Lay all the cards out in a grid with the colour side up.## How to Play

### Steps

See if you can make the times tables of the single digit cards (2, 3, 5 or 11). Line them up in order, 1 by 1.

You don't have to get them all, just try up to the 5th number or 6th. Now imagine instead doing the 7 times table.

- First colour in the 7. It's a prime number so it only has one disk.
- Now, what would 2 x 7 and 3 x 7 be? How many of them can you work out
- Once you've found a few of the 7 times table, write the numbers in on the back of the card

## What maths are we practising?

We are trying to get a feel for the fundamental theorem of arithmetic. We need an entirely new disk to make any multiple of 7. 7 is a prime number and is shown with a purple disk. So any numbers that are multiples of 7 will need a purple disk too.

By building this times table, you get to see primes as the building blocks of the number system.

Once you've done the 7s, find the smallest number that's not in the pack or the cards that you've made and you've got your next prime number!