Here we are moving on to some quite tricky subtraction: taking a single digit from a multiple of ten. Before attempting these four pages children should be confident with counting up to 100 and counting in tens up to 100. There are several ways that these questions can be tackled using mental methods. To begin with children will probably start with the whole hundred and count back in ones. Of course, they must know the tens number below the starting number to do this. Children who have a good knowledge of pairs of numbers that make 10 will be able to take from ten in their heads, hold that answer, take ten from the original number and then add the answer they are holding in their head. e.g. 40 - 6. 6 from 10 is 4. Take 10 from from 40 is 30. Add 4 to 30 is 34. Or.... the way I do it is to take 10, keep that answer in my head, work out the difference between the single digit and 10 and add it to my answer. e.g. 40 - 6 Take 10 from 40 is 30. 6 from 10 is 4. 30 plus 4 is 34. Life's just so tricky!! Try to work out how you do mental arithmetic as it is surprising the many different methods adults use. Go to our Subtracting a single digit from a multiple of ten pages.