This activity uses an interactive abacus to help develop and reinforce pupils' understanding of place value using hundreds, tens and units.

The activity has two areas; a free area where pupils can explore 3 digit numbers and a fixed questions area where pupils are faced with set tasks to carry out.

The questions area is useful for teacher assessment of place value understanding. The free area allows for teacher creativity in developing the fundamentals of place value whilst allowing opportunities to set illustrations or problems to support the pupils' specific needs.

Pupil Notes

An abacus was an ancient tool used for counting and carrying out calculations long before the days of calculators and computers. It consisted of a wooden frame with 'rods'. Beads were dropped onto the rods to represent numbers. The right-hand rod was for units (0 to 9) the centre rod for tens (10 to 90) and the left-hand rod for hundreds (100 to 900).

A single bead dropped onto the left-hand rod meant 100. If there were 2 beads on the left rod, 3 on the centre and 5 on the right the number would be 235.

In some countries the abacus is still used in everyday life to perform quick (and sometimes even quite complicated) calculations. What else can you find out about the abacus?

The online abacus will help you develop your understanding of hundreds, tens and units.

The main screen allows you to choose between a practice area or a set of computer generated questions to test your knowledge.

The practice area is where you can drag and drop beads onto an abacus and see how the numbers change as more beads are added. Try making numbers like one hundred and two, or four hundred and fourteen to see in which columns (hundreds, tens and units) you need to place the beads.

Once you have practiced making up different numbers you can try the 'question' area. Here you will be asked a set of number problems to solve. Some are quite simple but be careful, not all of them are as easy as they may seem! Once you have placed your beads on the abacus, click the 'check' button to see if you were right before moving on to the next question.

You could also try making up your own problems and asking a friend to use the practice area to try and solve them.

Why not explore adding numbers together with the abacus as well? Start with a number and then add more beads which make up the number you want to add. Count all the beads to see your new number. How could you use an abacus for multiplication?

Why not make your own abacus? You could make a really large one for the whole class by using cotton reels instead of beads and lengths of dowel for the rods. If you added more rods you could make really big numbers with thousands and tens of thousands. By placing a movable point on its base (maybe a piece of Blu-Tack) you could even make your abacus into a decimal one.