# Maths KS2: Multiplying using written methods

Finding themselves in space, Olivia and Hassan watch mathemagician Hypatia perform long multiplications in the sky by bending the stars.

After watching in awe, Archimedes comes to their aid and encourages them to bend the stars in the same way to perform a long multiplication written equation.

They find that placing the stars on top of each other, as with numbers, they can break down large multiplications and more easily find the answer.

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:

• Times tables up to 12x12
• Multiplying by 10 and 100
• Multiplying two digit numbers by partitioning

During watching the film

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

• What does each digit in the number represent?
• Why does a zero appear in the second calculation? What’s different?
• What good mistake might people make when doing short and long multiplication?
• Can you answer Hypatia’s final question by working out the answers before finding her mistakes?

Final question:
Can you spot the mistakes?

• 942 times 76 equals 69,582
• 326 times 48 equals 3912

• 942 x 76 = 69582 (two lots of regrouping not added). The answer is 71,592 / 326 x 48 = 3912
• (Second calculation not multiplied by 10). The answer is 15,648.

Following on from the film

• Link to rounding to encourage pupils to check their answers by using estimation, e.g. check 207 x 29 by doing 200 x 30, so it will be roughly 6000.
• Add another skill by setting comparison questions, i.e. crayons can be bought individually for 29p or a pack of 6 costs 149p. Arvind buys 42 individual crayons and Bill buys eight packs of crayons. Who spends more money? Record your answer using < or >.
• Link to area by finding the area of rectangles with large measurements, e.g. a football field measuring 252 feet x 94 feet, or even the area of composite shapes with large measurements.

### Curriculum Notes

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