 Let us see how we can compare two fractions using cross multiplication. So what we do in this method is that we multiply numerator of the one of the fractions to the denominator of the other fraction. So for example let's say we have these two fractions 2 by 3 and 1 by 4 and we just need to tell which fraction is greater. How we start is that we take numerator of one of the fractions with denominator of the other fraction and we multiply and we do the same thing for the other pair of numerator and denominator. So let's say we multiply 2 with 4 2 times 4 and we have written the multiplication below the first fraction because that's where we have got the numerator of it and we will write the other multiplication 1 times 3 and we are writing that below the other fraction because that's where we have got the numerator of it. Let's complete the multiplication 2 times 4 is 8 1 times 3 is 3 because the left hand multiplication is greater here and we can clearly see that it is greater than 3 2 by 3 will be greater than 1 by 4. This method works because when we compare two fractions we want to make the denominators of these two equal. So on the right hand side I'll just show you how this works when we want to compare 2 by 3 and 1 by 4 we will multiply numerator and denominator of the first fraction by the denominator of the other fraction and so what we write is 2 times 4 divided by 3 times 4 and we change the second fraction as follows. We write 1 by 4 and we multiply the numerator and denominator of the second fraction by the denominator of the first fraction and basically you see that the denominators remain equal but what we have done here 2 times 4 is exactly what we have done here and 1 times 3 is exactly what we did here as well. So basically we are just comparing the numerators when the denominators become equal and that's why this method works. Let's quickly see another example. So let's say we have minus 3 over 8 and comparing it with minus 5 over 12. So let's multiply minus 3 and 12 and on the right hand side we will multiply minus 5 and 8. The multiplication on the left hand side is minus 36 while the multiplication on the right hand side is minus 40 and we can see that minus 36 is greater than minus 40. So we can put this sign here and therefore the original fraction minus 3 by 8 is greater than minus 5 by 12. Remember you should put this multiplication below the fraction where the numerator of it is involved in the multiplication otherwise there is a chance that you will switch the places and you will get the wrong answer and this is how we compare two fractions using cross multiplication.