Maths KS2: Mental multiplication

While exploring a jungle, Olivia and Hassan learn the true nature of square numbers as being created when two of the same number are multiplied together.

Baffled at the thought of a square number, Oliva and Hassan start by mistakenly looking for numbers which look like squares.

With the direction of Archimedes however, they learn the true nature of square numbers as being created when two of the same number are multiplied together.

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:

  • Repeated addition as multiplication
  • Times tables up to 12
  • Multiplication and division represented by arrays

During watching the film

Depending on the focus of the lesson, you might wish to pause the film in certain areas to check for understanding, asking questions such as:

  • What other square numbers are there?
  • How would you define a factor?
  • How would you define a prime number?
  • Is 1 a prime number?
  • Can you answer Hypatia’s final question?

Final question:
Is it always, sometimes or never true, that square numbers have an even number of factors?

Answer to the final question:
Square numbers never have an even number of factors! All the factors have a pair except a square, because its pair is itself. Take a look at square number 16. It has one less factor than 18, which is not a square number.

Following on from the film

  • Make square numbers by using counters and then explore the other factors these square numbers have. Explore the meaning of square. Remember, the square cannot have a hole in the middle.
  • Explore the patterns made by the different times tables by colouring them in on a hundred square. The 5 times table is just two columns of coloured-in numbers. Why is that? The 9 times table is a diagonal line going backwards. Why is that pattern made? Which times tables’ patterns are similar and why?

Curriculum Notes

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

More from Hypatia's Mathematical Maze

Adding and subtracting using mental methods
video
Adding and subtracting using written methods
video
How and why we round numbers
video
Using addition and subtraction in multi-step problems
video
Multiplying by 10, 100 and 1000
video
Factors, multiples and primes
video
Multiplying using written methods
video
Dividing using written methods
video
Recognising and comparing fractions
video
Adding and subtracting fractions
video
Multiplying and dividing fractions
video