Class IV & V - Mathematics by GenX-Education - Dailymotion

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00:00Hi kids! Today, we will learn how to add and subtract with like and unlike fractions.

00:09So let's get started.

00:12First of all, let's revise what are like fractions.

00:17Fractions with same denominators are called like fractions.

00:23Now, let's see how we add and subtract like fractions.

00:29Example. Here are two fractions, 4x5 and 3x5.

00:38We have to add them.

00:41We just add the numerators of like fractions to add the fraction.

00:48Like for adding 4x5 and 3x5, we just add the numerators.

00:56Adding the numerators, that is, 4 and 3, we get 7.

01:02So, 7x5 is a sum of 4x5 and 3x5.

01:10Denominators remain the same.

01:13We just add the numerators to add the like fractions.

01:19Let's have a look at more examples.

01:23Here, we have another example.

01:26We have to add 8x9 and 6x9.

01:31These are like fractions as the denominators are same.

01:35So, we just have to add the numerators.

01:40Adding numerators, that is, adding 8 and 6, we get 14.

01:47Denominator will remain the same.

01:50So, the sum of fractions 8x9 and 6x9 is 14x9.

01:58Now, let's see how we subtract like fractions.

02:04Here, we have an example.

02:07We have to subtract 6x9 from 8x9.

02:12These are like fractions as denominators are same.

02:16Both are 9.

02:18We just have to subtract the numerators to subtract the fractions.

02:24Subtracting the numerators, that is, subtracting 6 from 9, we get 2.

02:31So, 2x9 is the difference between two fractions, 8x9 and 6x9.

02:40Here, we have another example.

02:44We have to subtract 6x4 from 9x4.

02:49These are like fractions as denominators of both the fractions are same.

02:56We just have to subtract the numerators in order to subtract the fractions.

03:02Subtracting the numerators, that is, subtracting 6 from 9, we get 3.

03:09So, our answer is 3x4.

03:133x4 is the difference between two fractions, 9x4 and 6x4.

03:21So, adding and subtracting like fractions is very simple.

03:26Now, let's learn how we do addition and subtraction on unlike fractions.

03:34Let's first learn what are unlike fractions.

03:39Fractions with different denominators are called unlike fractions.

03:44Here, we have two unlike fractions, 2x3 and 3x4.

03:51Their denominators are different, so we can't add them directly, that is, by just adding their numerators.

03:59So, let's see how we add them.

04:03For adding the unlike fractions, first we have to convert them to like fractions.

04:09That is, we have to make their denominators same.

04:13And then we add them like and like fractions.

04:18Now, we will make the denominators same using the crisscross method.

04:23Now, let's see what is the crisscross method.

04:28In this method, we multiply both the numerator and denominator with the denominator of other fractions.

04:37Like here, multiply both the numerator and denominator of 2x3 with 4.

04:45And multiply both the numerator and denominator of 3x4 with 3.

04:52So, it looks like a crisscross.

04:564 multiplied with 2, we get 8.

05:004 multiplied with 3, we get 12.

05:043 multiplied with 3, we get 9.

05:084 multiplied with 3, we get 12.

05:12So, we got 8x12 and 9x12.

05:17Now, these two fractions are same as their denominators are same.

05:24Now, we can add them like like fractions.

05:28We just have to add the numerators to add them.

05:32Adding 8 and 9, we get 17.

05:36So, 17x12 is our answer.

05:41Now, let's take another example.

05:44We have to add these two fractions.

05:486x2x3 plus 7x4.

05:53Here, one of the fraction is a mixed fraction.

05:57So, first we convert the mixed fraction to an improper fraction.

06:02We multiply the whole number with the denominator and add numerator to it.

06:09Denominator remains the same.

06:12So, multiply 6 by 3 is 18.

06:17We have converted the mixed fraction to an improper fraction.

06:22Now, we have two unlike fractions to add.

06:26We have to add 20x3 and 7x4.

06:32We learned that we need to convert unlike fraction to like fractions before we add them.

06:38That is, the denominator should be the same.

06:42Now, use a crisscross method to make them like fractions.

06:48Now, we will multiply both the numerator and denominator of 20x3 with 4.

06:56And, we will multiply both the numerator and denominator of 7x4, denominator of other fraction.

07:06So, multiply it with 3x3.

07:11So, it becomes our crisscross.

07:1520x4 equals 80.

07:193x4 equals 12.

07:23So, it becomes 80x12.

07:273x7 equals 21.

07:323x4 equals 12.

07:36So, it becomes 21x12.

07:41Now, we have two like fractions to add.

07:44And, we know adding like fractions is easy.

07:49Just add the numerators to add the fraction.

07:53And, adding 80 and 21, we get 101.

07:58So, the answer is 101x12.

08:04Now, let's learn an example where we will subtract a like fraction.

08:10First of all, we always subtract the smaller number from the bigger number.

08:15So, same as for fractions.

08:19Always subtract the smaller fraction from the bigger fraction.

08:24Now, let's subtract two unlike fractions.

08:28We have to subtract 5x9 from 2x6x7.

08:34That is, we have to subtract 5x9 from a mixed fraction.

08:41So, first we convert the mixed fraction to an improper fraction.

08:46For that, we will multiply 7x2 and then add 6 to it.

08:537x2 equals 14.

08:5814 plus 6 equals 20.

09:03Denominator remains the same, so its improper fraction is 20x7.

09:10So, we have to subtract 5x9 from 20x7.

09:15So, these are unlike fractions.

09:19So, first we use the crisscross method to convert them to like fractions.

09:25In the crisscross method, what we will do is multiply 20x7 with 9x9.

09:34That is the denominator of the other fraction.

09:38And multiply 5x9 with 7x7.

09:43That is the denominator of the other fraction.

09:4720 multiplied with 9, we get 180.

09:529 multiplied with 7, we get 63.

09:565 multiplied with 7, we get 35.

10:019 multiplied with 7, we get 63.

10:06Now we have two like fractions.

10:09And we can subtract the numerators to subtract the fraction.

10:14Subtracting 35 from 180, we get 145.

10:21So, 145 by 63 is our answer.

10:27So kids, now you know how to add or subtract like and unlike fractions.

10:34Now you may go ahead and take a quiz to learn more.

10:38Bye-bye.

Adding And Subtracting Like And Unlike Fractions

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Class IV & V - Mathematics

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