This is an easy to organise investigation suitable for children in Year 3 onwards. The initial task is to use each of the digits 1, 2, 3 and 4, once only, to make as many addition sums as you can. For example: 12 + 3 + 4 = 19 2 + 413 = 415 To complete this investigation successfully children need to be confident with simple addition and be able to add a single digit to a hundreds number, as well as adding two, two digit numbers. Probably the best way to start this investigation is to look for all the addition sums that can be made by adding a single digit to a tens number. Thus, working in a logical order can be encouraged, by looking for all the 3 digit numbers that can be added to one: 1 + 234     1 + 243    1 + 324     1 + 342     1 + 423    1 + 432 then continuing with 2, 3 and 4 in turn. It would be useful to show this methodical way as part of the class introduction to the investigation - inviting children to find all the sums which involve an addition of one to a three digit number. Hopefully they will note that there are 6 possibilities, and this should help them when adding 2 to a three digit number. Whilst doing this children can also be looking for the largest and smallest possible answers. Children should also be clear that: 1 + 2 + 3 + 4 is the same as  4 + 3 + 2 + 1 Go to Adding Digits investigation