How to Reduce Fractions

Video Transcript

"Hi, I'm Steve Jones, and I'm going to tell you how to reduce fractions. The reason we have to reduce fractions, is because fractions come from real information. So, for example, if somebody comes, and tells you that sixteen out of the twenty-four cars in the car park are green, then it doesn't mean very much, sixteen out of twenty-four. But you should know, in a real fraction, what it is. Let's have a look at these fractions. Here's several fractions, sixth eighths. Sixth eighths is not a fraction that we normally would deal with. Let's look at six and eight. What number divides into both? And, that is what we're going to do to reduce it. Well, we know that two will divide into both of these numbers. Let's divide two into them. So, two into six, goes three, two into eight goes four. So, in fact sixth eighths is three quarters. So, if we say, in the car park, three quarters of the cars are black, that is, six out of eight cars. OK, we went into a shop, and seven out of the fourteen pieces of fruit, were apples. Well, this is not a difficult thing, cause we spot straight away that fourteen is actually two sevens, so we can cancel with seven, divide by seven here. So, in fact we're saying, half are apples. Right. We go into school, and we say in the classroom, sixteen of the twenty-four people, happen to be girls, in the class. So, what proportion is this, sixteen girls out of twenty-four members of the class. Well, we know sixteen and twenty-four, well, they both divide by four. Don't they? So, four sixes are twenty-four, and four fours are sixteen. But, looking at this, hold it, they still divide by two. So, four divides by two, and six divides by two. So, in fact, two thirds of the classroom, is full of girls. And, finally, we're in school, and we know that a hundred and twenty-five out of the two hundred and twenty-five people are girls. Good example again. So, what proportion is this? We reduce the fraction, we can see here, this is bound to divide by five, so five's into twelve goes two, five's into twenty-five, that's twenty five. And, two hundred and twenty-five, well, five's into twenty-two, goes four fives are twenty, I think that's forty-five. So, twenty-five divided by forty-five, ooh, this reduces yet again, by five. So, divide that by five, I'll get five. Divide this by five, I'll get nine. Nine five's are forty-five. So, in fact, five ninths of the whole school is girls. This is why we have to be able to reduce these proportions. Because the numbers we're getting to give us the fractions are not simple, small numbers, they're big numbers. And, we can reduce them, in this way, to get a fraction, which we can use in our normal conversation. That's simply how to reduce fractions."