The Highest Common Factor (HCF) and the Lowest Common Multiple (LCM) are easy once you get used to the names.

• HCF of 8 and 12 is 4. The HCF is smaller than the numbers.
• LCM of 8 and 12 is 24. The LCM is larger than the numbers.

Page with notes and interactive exercises :: you can try to answer the questions as you go along and then check your answers. This page explains both the ‘common sense’ method and the ‘prime factors’ method.

The links below might help. These links have buttons to click on the page, so you can get instant marking on examples.

• About Factors and Prime Numbers
• Finding the prime factors of a number using ‘factor trees’
• Prime Factors quiz from BBC Byte Size

The adding and subtracting games from the BBC Skillswise site use an interesting approach to ’splitting’ the numbers down into 100s, 10s and units. Try this, but watch you don’t get confused. There is also a multiplication game.

For those who are confident, try these multiplications - you can click at the bottom to get the answers. Try these long divisions.

This tables game from the BBC Skillswise site is quite good if you need practice. (The game opens in a new Window, just close the window to return here).