By Year 6, children are increasingly efficient at manipulating numbers mentally in order to carry out multiplication and division. They can double and halve large numbers, estimate to check that their answers to calculations are reasonable and explore different methods for multiplication.
Besides practicing on whiteboards to multiply large numbers, up to 4 digits x 2 digits, they have been working in the context of money in real- life situations. They have also used alternative techniques to check that their answers are correct and through continued rigour, developed both their accuracy and speed.
Children have chosen the most efficient method for a given calculation and have come to appreciate that it is valuable to look at the numbers being used before choosing their technique. Many concluded that their mental methods often gave the most accurate answers.
In particular, they have enjoyed the challenge of comparing different methods from around the world, past and present. The have made links between the Russian and Egyptian methods, which both involved doubling and halving of large numbers. They have explored the Gelosian method which links with the use of Napier’s bones, created by the Scot, John Napier. He invented strips (originally made from bone) about 400 years ago to help calculate multiplication and division. It has been fascinating to discuss the merits of each system of multiplication and to explain how they work.