Having a good knowledge of adding pairs of single digit numbers now leads on to adding pairs of multiples of 10, 100 or 1000. Plenty of practice is still needed with adding two or three small numbers, leading towards the end of the year to adding 2-digit numbers mentally. Written methods of addition are explained, including adding decimals, working towards the use of the standard written method, which we all recognise and love!
Whilst the new statutory requirements for Year 4 concentrate on developing written methods of addition there are still many important mental skills to develop and re-inforce. These include quick mental addition of three small numbers and the addition of two 2-digit numbers mentally.
A technique which is particularly important is adding the nearest whole ten and adjusting. An example of this can be seen when adding 47 and 38. An easy way to do this is add 47 and 40 making 87 and then adjusting by subtracting 2 to make 85. Done! This is probably an easier way than adding the 7 and 8 and then adding the tens.
When adding several small numbers it is always useful to look for pairs that make 10. This works because addition can be done in any order.
For example 7 + 8 + 3 = ? is done easily by adding 7 and 3 to make 10 and then adding the 8 to make 18. By Year 4 children should know by heart all pairs of single digits which add up to 10.
Another powerful technique is to use the knowledge that addition and subtraction are the inverse of each other. Knowing the fact that 47 + 38 = 85 immediately gives several other pieces of information, such as 85 – 38 = 47 etc.
For many years primary school maths teachers have discussed whether to use squared paper or not for written addition, subtraction etc. If you were in school 50 years ago it is very probable that you had a maths book with paper made up of squares. More recently children are expected to work with ordinary lined paper, or even plain paper. Teachers argue that using graph paper or squared paper does not help for developing number concepts. It might keep things neat but when a child puts a 6 in one box, a 5 in the next and a 3 in the next they are just writing 6-5-3 and not six hundred and fifty three.
Others argue that the child is more likely to understand the value of each digit using squared paper, especially if the columns are marked (e.g. H T U). Another argument in favour of squared paper is that it is a help for children who have problems lining things up when writing (e.g. Dysgraphia). This could be very important as written addition and subtraction are now being introduced at an earlier age.
We have written calculations on both plain paper and squared paper.