This content was created by Rob Langman. This content was uploaded by Rob Langman. This is a YouTube instructional video titled "How to Work Out Unknown Values on a Number Line or Scale" (created 2024-04-10). A single presenter (identified as Ellie / SPEAKER A) explains strategies for teaching primary pupils to find missing values on number lines. The presenter walks through two examples—one for lower Key Stage 2 (finding values between 0 and 75 by dividing the difference by 3 to get steps of 25) and one for upper Key Stage 2 involving decimals (finding values between 1 and 1.8 by dividing 0.8 by 4 to get steps of 0.2), and emphasizes understanding equal parts and correct decimal notation.
Chapters
Hi, I'm Ellie and in this video we're going to look at how you can help your pupils find unknown values on a number line. We're going to look at two examples, one more appropriate for lower key stage two, and one that you might use with year five and six. So let's start with this one here. Now, this is something that you might see given to year three or four. We've got a scale and we've got some missing numbers and the pupils need to find these numbers. Now, you can help pupils to understand that there is a simple process to working this out. What you want to begin with is by asking them, what values do we know? So you can point out that we know that this is zero, we know that this is 75. So the first thing we want to do is think about what is the difference between these two numbers, 0 and 75? And hopefully pupils know that when you talk about difference where you can use subtraction, so 75 takeaway, 0 is 0. That's quite a nice easy one to start with. You then want them to see, what values do we need to find in between? How many values do we need to find? So we've got a value here that we don't know and another one here. In total, there are 1, 2, 3 equal parts between 0 and 75. The equal is really important because that helps the pupils understand what they need to do to find out how much each of these is worth. So this whole gap is 75. We've got three equal parts. If you ask them, how do I know how much each of those equal parts is worth, they should be able to know that they've got to do 75 divided by 3 to find out what each equal part is worth. Now, they might be able to do that mentally, or you could go to written division, but they should get to an answer of 25, which means that you can pop your answers on the scale then. So you know this one is 25. If each part is worth 25, then 25 and 25 is 50. So they know that the pattern is that we're adding on 25 each time. So we had two steps. The first was to identify the difference between the known values, and the second was to divide that difference by the number of equal parts between those two known values. And we can apply that to other questions. So if we look at this one, which is a bit tricky and maybe something that you'd see in upper key stage two, because we're involving decimals, we can apply the Same rules our two known values are 1 and 1.8. So our first step was to find the difference between those two. The difference difference between 1 and 1.8 is 0.8. And then we're going to look at how many equal parts are between those two values. 1, 2, 3, 4. So we need to divide our 8/10 0.8 by 4, which will give you 0.2. So now we just know that to fill in the unknown values we need to go up by 2/10 each time or, or down by 2/10 if we're going that way on the number line. So pupils should then be able to do this as 1.2, 1.4, 1.6, 1.8, this one make sure that they don't start doing this 1.10, that is not 1.8 at 2:10. So they need to know that that goes up to 2 and here again you're crossing the boundary of the ones. So it's going down to 0.8. And that's a method that you can use with your pupils to help them find unknown values.
