A short YouTube lesson (presented by Rebecca) introducing the mathematical order of operations for primary-school pupils. The video demonstrates how different orders produce different results (example: 2 + 12 × 3), explains the BIDMASS/BODMAS acronym (brackets, indices, division, multiplication, addition, subtraction), works through a longer expression step-by-step (using brackets, division, multiplication and subtraction), and recommends classroom strategies—tick-off method and a hierarchy triangle—while emphasising left-to-right handling of multiply/divide and add/subtract.
Chapters
Hi, I'm Rebecca, and in this film we're going to look at the order of operations. Now, some calculations contain more than one operation, and it's important that we teach children to recognise that actually the order that they do it in will have an impact on the answer. So let's see how to teach this. You could start by giving your pupils a calculation like this one here and asking them to start by solving it with the addition first and then the multiplication. So 2, add 12 is 14 and 14 times 3 is 42. Then ask them to repeat the calculation again, but this time start with the multiplication. So here we have 12 times 3 is 36, and then 36, add 2 is 38. By doing this, they can see that it has an impact on the answer that you get. And there is actually strict mathematical rules about the order and priority that operations take in a calculation. And this is called the order of operations. And we're going to use the acronym bidmass, sometimes known as bodmas, to help the children remember the order that you do them in. So let's have a look at an example. Here we have a very long calculation. We're going to use BIDMASS to solve it. B stands for brackets. So I'm going to do what's in the brackets first. And here we have two. Add five is seven. I'm going to write the answer to that underneath because I just find that it helps keep track of where you're up to. And actually, I teach my children to tick it off as well so that they know that they've checked, that they've looked for that part of the calculation. Then we have I, and I stands for indices. And I tell my children to think of little twos and little threes. So it's where numbers are squared or cubed. We don't have any indices in this calculation, so I can move on. The D stands for division, and I do have a division in this one. It's 16 divided by 2, which we know is 8. Then I'm going to look for some multiplication, and I do have a multiplication here as well, so I have 10. But this time I'm going to times it by the answer to the brackets 10 times 7, which is 70. And now I can finish my calculation because here I don't have an addition, but I do have a subtraction and 70. Take away eight would give us 62, and that tells us our answer. One really good way to help pupils remember this is also to use this triangle and it gives you the hierarchy that the order of the operations needs to come into. You'll notice that the multiply and divide and the add and subtract are on the same line of the hierarchy, and that's fine, but pupils need to understand that they need to do them from left to right in that order. So there you go. That's an introduction to the order of operations.
