Partitioning For Mental Addition And Subtraction

Hi, I'm Rebecca and in this film we're going to look at how to use partitioning to add and subtract mentally. Now, children often find it really difficult to do this because they lack confidence, so it's important to give them lots of opportunities to practice. So let's have a look at a problem here. We have 386, add 13. Now, I know I can do this mentally because the numbers in each column for place value will never go over 10. So I'm going to start with my ones column. So I have 13, I'm going to add three ones to six, which will give me nine. Then I'm going to look at my tens. I have 80, add 10, which gives me 90. And then I have 300. And I'm not adding anything onto that. So I'm just going to stick with 300. And then I can quickly and easily see that My answer is 399. This strategy also works with subtraction. Again, I can see that I'm not going to need to cross any boundaries, so I can do it mentally. And I'm going to carry on using jottings, which is fine, so that children don't get lost. I'm going to start with the hundreds. It doesn't matter which order you do it in. So I've got 500, take away 100 will give me 400. Then I have 30, take away 30, which will give me zero. I'm going to put the zero on there. And then I have seven, take away three, which is going to give me four. So I can quickly see that my answer is 404. Now, some children will be able to spot straight away that 37, take away 33 will actually give us an answer of four and we'll come to the answer quicker. So there you go. That's using partitioning to add and subtract mentally.