How to Take LCM in Adding and  Subtracting Fractions | LCM Method for Fractions - video Dailymotion

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Transcript

00:00In this video, we are going to discuss that how to take LCM while adding or subtracting fractions.

00:07So many students got stuck in this step when they are going to add fractions or subtracting

00:13fractions and they have to find LCM of the denominators. So in this video, I will tell

00:18you very easy method, easy trick. So sometimes we don't need to find LCM by the factorization,

00:24we can find it by direct multiplication. So let's start. We have a question here,

00:297 upon 5 plus 5 upon 7. So first you observe the denominator, we have first denominator that is 5

00:37and second denominator is 7. So you can observe that 5 has only two divisors, 1 and 5. And also

00:457 have only two divisors, 1 and 7. So these both numbers have no common divisor, no common factor

00:52except 1. So it means that we don't need to factorize these numbers and find LCM by factorization.

00:59Simply you have to multiply, you can multiply directly 5 times 7 and you can get the LCM that is 35.

01:07Okay, our LCM is 35. So next step is very crucial. We have to put the equal sign and then we have to put

01:15a long bar that we have to complete the procedure of addition of fraction. And we can write this LCM

01:22as a denominator in the next fraction. Okay, so next step is very important. Now you have to check that

01:29in the first fraction, we have denominator 5. So we have to identify that how many times 5 goes into 35.

01:37So you can check 5 times 7 is 35. It means that 5 goes into 35 7 times. So we have to multiply this

01:44number with this number with the numerator. So we have already 7. So we can multiply 7 with this 7.

01:51So 7 times 7. Then we have sign up addition. We can put sign up addition. And then you move to

01:58second fraction and second numerator. We have 7. So now you check how many times 7 goes into 35.

02:05So clearly 7 times 5 is 35. It means that 7 goes 5 times into 35. So we have to multiply this 5 with the

02:14numerator of second fraction. So again we have same number of multiplication 5 times 5. So this is

02:21done. Now you can multiply and simplify the answer. 7 times 7 is 49 plus we have 5 times 5 is 25.

02:29So now you can add this number and our denominator will be 35. So we have 74 divided by 35. So this is our final answer.