1. Know addition and subtraction facts Children should be familiar with two-digit addition and subtraction involving multiples of 10. e.g.  80 + 30   or  250 – 60 They should be able to add or subtract multiples of 100, crossing 1000. e.g. 600 + 900   or  1 400 – 800. They should be able to add/subtract a two digit multiple of ten to/from a two or three digit number without crossing the hundreds boundary. e.g. 65 + 20  or   669 – 40. They should be able to add a two or three digit number to a multiple of 10, 100 or 1 000. e.g. 70 +16   or  560 + 32. They should also be able to complete statements such as ???  + 4 500 = 5 000 In year 4 children are expected to be able to calculate mentally using  a variety of methods. They are also expected to explain their methods, both orally and in writing. Further skills involved are: a.    adding a single digit to a three or four digit number, crossing the tens boundary e.g.   365 + 8 = b.    subtracting a single digit from a three or four digit number, crossing the tens boundary e.g.   363 - 7 = c.    subtracting a single digit from a whole 100 or 1 000 e.g.  1 000  -  7 = d.    find the difference between two numbers which are close to a whole thousand, but either side of it e.g.    3 005  -  2 998 = e.    find what needs to be added to a whole hundreds number to make it up to the next thousand e.g.   4 500  +  ???    =  5 000 f.    By the end of the year, add or subtract any pair of two digit numbers e.g.  36  +  46 =     or    83  -  27 = All methods used must be explained by the child, in words and writing. 4.  Checking answers Techniques for checking calculations need to be developed. It is very easy for children to assume that because a calculation is done on a calculator, it must be correct. Their faith in the electronics is probably justified, but what about their faith in their own abilities? There are several methods that can be used: a) Doing the inverse operations. If a subtraction has just been calculated, do the opposite addition to check. eg.  180 - 50 = 130          Check by doing 130 + 50 to see if it comes to 180 b)  Checking a total by adding the numbers in reverse order. eg.  23 + 31 + 17 + 62 = 133 Does 62 + 17 + 31 + 23 also equal 133 ? c)  Doing an equivalent calculation. eg.  182 + 36 = 218          Check with (say) 100 + 40 + 40 + 2 + 30 + 6 or  180 + 30 + 2 + 6 d)  Perform an approximate calculation to see if the answer is in the correct range. eg.  389 + 105  = 494       Check:  400 + 100 = 500 e)  Carry out some simple tests such as the sum of an odd number and an even number is always an odd number. Go to Know Addition and Subtraction Facts in Year 4