Prime Numbers and Factors

The link for the ppt for the puzzles below

PrimesDsCUkKHXgAAhmCk (1)



There are so many great resources for students to look at factors and primes. Depending on set and age, I have used many varied problems and questions. Sometimes I start with Squares, Sticks or Rectangles. For this task students take 1 square and they have to arrange it as a square, if this isn’t possible they try a rectangle with length greater than one, if this isn’t possible they draw a stick (one dimension can be 1). So they draw a square for 1, sticks for 2 and 3, then a square for 4, stick for 5, a 3×2 rectangle for 6, a stick for 7 and so on.


Another way I like to start this topic is with this question


Students start discussions of divisibility and more often than not students mention primes. This question is also nice when looking at sequences. Students think about generating a list of possible numbers and it starts conversations about which numbers can be used ‘it will be odd as cant divide 2 exactly’


Once students are familiar with the terms ‘factors’ and ‘prime’ I like to move one to some problems where it tests their abilities to determine whether a number is a prime or what factors it has.


I usually use the above task as a plenary task which you’ll find on the ppt below and I sometimes restrict the numbers and other times allow them to use any number.


Types of Number

Types of Numbertyp3typ2

The two task above are from the worksheet below and students have to think about factors of numbers but it also introduces HCF and finding common factors of two numbers.

Factor 2 Way Tables

I usually finish with a task like below and although you get the students picking out 20 because its the only EVEN you do get students using ‘factor of’ and ‘not a prime’

It leads to some interesting discussions.


This proved an interesting starter. Some students filled it in then realised it didnt add up to 15!


Updated for Christmas!

A simple dot to dot snowflake for students to do as a starter

Dot to DotTypes of Number Dot to Dot

Screenshot 2020-07-04 at 23.13.17Screenshot 2020-07-04 at 23.13.25Similar Shapes

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