In order to add or subtract fractions that have different denominators, we need to find a ------------ denominator. It is important to realise that any fraction of the form a/b can be multiplied top and bottom by the same ---------- and still have the same ------------ . For example, 3/5, 6/10, 9/15 and -------------- are all the same fraction. We can recover the original form of the fraction by dividing top and bottom by the same whole number. For example, 9/15 can be changed to 3/5 by dividing top and bottom by ------------ . The simplest way to find a common denominator is to ---—-------- the denominators of our two fractions. For example, a common denominator of 2/5 and 1/3 is 15. We then have to find the equivalent fraction that we are adding or subtracting with this denominator. In this case, we want to express both fractions as fifteenths: 2/5 is equal to 6 fifteenths, and 1/3 is equal to ------------- fifteenths. Now that they have the same denominator, we can add them, giving a total of 11 fifteenths.

In order to add or subtract fractions that have different denominators, we need to find a common denominator. It is important to realise that any fraction of the form a/b can be multiplied top and bottom by the same number and still have the same quotient . For example, 3/5, 6/10, 9/15 and 12/20 are all the same fraction. We can recover the original form of the fraction by dividing top and bottom by the same whole number. For example, 9/15 can be changed to 3/5 by dividing top and bottom by 3. The simplest way to find a common denominator is to multiply the denominators of our two fractions. For example, a common denominator of 2/5 and 1/3 is 15. We then have to find the equivalent fraction that we are adding or subtracting with this denominator. In this case, we want to express both fractions as fifteenths: 2/5 is equal to 6 fifteenths, and 1/3 is equal to 5 fifteenths. Now that they have the same denominator, we can add them, giving a total of 11 fifteenths.