# Maths KS2: Factors, multiples and primes

Trapped in a desert together with Archimedes, Olivia and Hassan learn what common factors, multiples, and prime numbers are.

However, before they can leave the desert, our great mathemagician Hypatia appears and asks what the similarity is between three numbers: 3, 7, 13.

After realising that these are prime numbers, Hassan and Olivia can move onto the next section of the maze.

This short animated film is from the BBC Teach series, Hypatia's Mathematical Maze.

### Teacher Notes

Before watching the film

Prior to this lesson you may wish to introduce students to other relevant topics, for example:

• The times tables up to 12x12
• Multiplication and division as repeated addition and repeated subtraction
• Multiplication and division represented as arrays

During watching the film

Depending on your lesson’s focus, you may wish to pause the video at certain points to check for understanding, asking questions such as:

• What else is 3 a factor of?
• What multiple do 3 and 7 have in common?
• How would you describe the terms ‘factor’ and ‘multiple’?
• How do you know that 3, 7 and 13 are prime?

Final question:
I am thinking of two two-digit numbers. Both of the numbers have a digit total of 6. Their common factors are 1, 2, 3, 4, 6 and 12. What are the numbers?

Answer to the final question:
24 and 60

Following on from the film

• Pause the video to give time for pupils to complete Hypatia’s final question
• Ask pupils to draw factor bugs, which are little drawings of bugs with the right number of legs and antennae to match the number of factors of a given number. The antennae are the number itself and 1. A square factor is always a tail. The class is then asked to fill in the missing factors.
• Explore common multiples by giving the pupils hundred squares. Ask them to colour the multiples of 2 and circle the multiples of 3. Some numbers have been coloured and circled. What do you notice about these numbers? (They are the multiples of 6)
• Look at some large numbers. Can any of these be prime? How do you know? E.g. 276 (not prime because it’s even), 145 (not prime because it has a 5 at the end so it’s in the 5 times table), 333 (not prime because it can be divided by 111), 471 (not prime because it has a digit total of 12, meaning it is in the 3 times table).

### Curriculum Notes

This short film is suitable for teaching maths at KS2 in England, Wales and Northern Ireland and 2nd Level in Scotland.