A Year 6 / Key Stage 2 instructional video transcript in which Clare demonstrates using bar models to solve a fraction problem: three-quarters of Lisa's money equals one-half of Mark's, and together they have £120. Clare partitions bars into quarters and halves to show there are ten equal 'quarters', so each quarter is £12, yielding Lisa £48 and Mark £72; she then verifies the totals sum to £120.
Questions this video answers
£120
Three quarters of Lisa's money equals one half of Mark's money (3/4 of Lisa = 1/2 of Mark).
£48
£72
£12
Chapters
Hello, I'm Clare and today we're going to look at bar modelling again to see how we can solve the problem. Some more complex problems where you need to find unknown quantities when we've only been given some fractions. Let's have a look at the problem. Well, this time Lisa and Mark have been saving their money and putting it into money boxes. It says three quarters of Lisa's money has the same value as half of Mark's money. Altogether they have £120. How much does each child have? Now, it's worth practicing these questions because these are the sorts of questions at key stage two, your year six children can get three marks for. And if you draw them as a bar, it makes it so much easier. So I've just started this because I'm beginning to look at this problem and I want to draw a bar to represent Lisa's money. It says three quarters of Lisa's money has the same value as half of Mark's money. So I'm going to divide Lisa's money up into quarters by doing that. I'm going to do that by drawing three lines. There we are. Now, I know that Mark has the same amount as 3/4 of Lisa's money, so I've already lined my bar up to match up with three quarters of Lisa's money. I'm going to put those quarters in so I can see where they are. But this is only half of Mark's money. So I need to draw the other half of Mark's money. There we are. And I'm going to do the same thing. I'm going to put the same amounts in, so I'm going to divide that into quarters as well and he'll have another three quarters in the second half of his money. Now, looking back at the problem, it actually already tells me that both children, all together, their money is 120 pounds. So I know this adds up to 120. Right now this is the bit I need to look at it to work out how much money does each child have? Well, I can see all together we have got 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 quarters. So I've got 10 quarters, which makes £120. Now, at this point I'd ask children if you know that 10 quarters is 120, how much? How can we work out how much one quarter is? And I hope they would be able to tell me that you need to take 120 pounds and divide it by the 10. And if I do that, I'm going to get 12 pounds. Now, I know that each quarter is 12 pounds. I'm going to put that on my bar model. So I've got £12 there, £12 there. It's important to do this so that the children can see exactly how much more money Mark has than Lisa. There we are. Now, next thing to say, always say to children, go back, reread the question. Have we answered the whole question? It says at the end of the question, how much does each child have? Okay, I need to do some more maths. OK, I need to look at Lisa. She's got 1, 2, 3, 4, lots of 12 pounds. So Lisa, let's put her here. She's got 12 pounds multiplied by four, which is going to be 48 pounds. Now let's look at Mark. He's got 1, 2, 3rd, 4, 5, 6, lots of 12 pounds. So he's going to have 72 pounds. Now the children have solved the problem, it's important to look back and think, let's double check. We've got that right. And I can do that by adding up the £72 to the £48. And I can check to see that I've got £120 altogether, which is correct. So that's how we use a bar model to solve more complex questions when we only know what the fractional relationship is.
