In this video we will add the fractions 1/4 and 1/5. First we need to find a common denominator both 1/4 and 1/5. Once we have a common denominator, we can easily find the sum by of the fractions by adding the numerators while keeping the denominator the same.
Note that the lowest common multiple (LCM) is also called the lowest common denominator (LCD). You can find the LCM for and by listing all the multiples for 4 and 5. Then you select the lowest number that is the same for both numbers.
If we look at the multiples of 4 and 5, we'll find that both 4 and 5 can be divided evenly into 20. So 20 is the lowest common denominator. We multiply the 1/4 by 5/5 to get 5/20. Then we multiply the 1/5 by 4/4 to get 4/20. We can now add these together to get 9/20.
A quick way to check your work is provided at the end of the video. When you add 1/4 + 1/5 you should get the same fraction for both methods.
