Applying decimals and percentages to area multiplication

Key Stage 3

Maths

Manipulating and calculating with fractions

Which fractions calculation is being shown here?

﻿Hello, I'm Mr. Langton and today we're going to apply anointed decimals and percentages to the area model of fraction multiplication, don't worry, it's easier than it sounds. All you're going to need is something to write with and something to write on. Try make sure you're in a quiet space with no distractions and when you're ready we'll begin. We start off with trying this activity, try fill in the missing blanks with the appropriate values. Pause the video to have a go, when you're done, unpause it and we'll go through the answers together. Pause in three, two, one. Here are the answers, hopefully there isn't anything too tricky here. In this example, we're going to show how we can use our area models to multiply 0.2 by 0.3. Now 0.2, is equivalent two tenths, and 0.3, is equivalent three tenths, so we can write those both as fractions, as two tenths multiplied by three tenths, and then once we got this start, we can now do the multiplication with the grid like we did before, we can see from the grid, that there are six squares shaded in, That over a 100. If you weren't using the grid, you going to have two tenths multiplied by three tenths, two times three is six, ten times ten is a hundred. So two different ways we can get that answer, we could turn that back into a decimal if we like, so we've got six hundredths, we get 0.06. Okay, now it's your turn to have a go, we're going to write each of these as a fraction calculation and as a decimal calculation. Pause the video and have a go, when you're ready unpause and we'll go through it together, you can pause in three, two, one. Okay if you had a go, let's see what we've got, looking at this first one here on the left hand side, we've got two parts shade out out of tenths, that's two tenths, which is also 0.2. And here we've got one, two, three, four, five, six, seven, seven tenths which is also 0.7, two tenths multiplied by seven tenths, is 14 hundredths which is also 0.14. Okay let's have a look at the one underneath. This time we've got three tenths, and all the way along here we've got eight tenths so as a decimal we're looking at 0.3 multiplied by 0.8 which is three tenths multiplied by eight tenths. And that'll be 24 hundredths or 0.24. Okay now for the top right, That shaded part there represents three tenths or 0.3. and here we're looking at seven tenths or 0.7 three tenths multiplied by seven tenths is 21 over a 100, so 0.21 and finally we've only got one square shaded there so that represents one tenth, and it's the same that way, that also represents one tenth and as such we're doing a tenth multiplied by a tenth, which is one hundredth, that's the decimal 0.1 multiplied by 0.1 is 0.01, now what I'd like you to do is pause it just for a moment, and look very carefully the answers especially the decimal ones. Look for any patterns and techniques that you can spot, any tips that you can use in future. This is really, really important part of decimal multiplication and if you get this you can do anything to do with decimals, so take your time, have a good look and see what you can do, when you're ready, unpause it and we'll move on. You can pause in three, two, one. Okay now it's time for the independent task. Now it starts off relatively straight forward starting with the one at the top, in part a, and part b. Once you get to part c and d, it's a little bit trickier because you need to start thinking about equivalent fractions. So once again, take your time, and look very closely at what you've got. The questions on the right hand side are all very, very similar. In fact in the first instance, they're all the same. 2.5 multiplied by 0.2, the trick is I want you to do it in four different ways, I'll give you a bit of lean and a bit of guide for how to get there, but you're going to have to really think carefully, to get as many different methods as possible for solving that problem. If you can get all four methods, give yourself a good big pat on the back because that'd be really good. So take your time, pause the video for a moment, have a go at the worksheet and we'll go through the answers after you're done. Good luck. So here are the answers, some of them were really tricky, so if you need to just pause this and have a close look at them, see how you got some, see if there's any corrections you can make and if you can see where you went wrong. This is the last activity, pick three numbers from the green boxes and place them in the empty spaces to make the calculations close to 50% as possible. Pause the video to have a go, make some notes and when you're ready unpause it and we'll go through it together. You can pause in three, two, one. So how did you get on, I came up with few options, I might get on that works, but it's a little bit cheating, I'm kind of using the same card twice, five tenths multiplied by nine tenths will be 45 over 100. Which is 45%, so I can get to exactly 50%, if I add on 5%. See the only way I could find, that makes exactly 50% I don't think there's another way, but perhaps you've got one. If we're going without using the same card twice, then there are two numbers we could use instead, we could put a six there which gets us close, that gets us 51% or if we put a four there, that one gets us to 49%. You might find some other ways, I think there are other ways of make 51%, so see what you've got, if there's anything else, I'd love to see them. So if you'd like to share those answers or anything else you've worked out today, please ask your parent or carer to share you work on Twitter tagging @OakNational and #LearnwithOak. Thanks.

Applying decimals and percentages to area multiplication

Applying decimals and percentages to area multiplication

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UnitMaths / Manipulating and calculating with fractions

Maths