DATA HANDLING CLASS 7| PART 2| EX 3.1| CLASS 7 |NCERT | INSIGHTFUL MATHS| EASY EXPLANATION
DATA HANDLING CLASS 7| PART 2| EX 3.1| CLASS 7 |NCERT | INSIGHTFUL MATHS| EASY EXPLANATION
Transcript
00:00hey everyone welcome to insightful maths today we are going to continue the
00:06session data handling I have already made one video earlier wherein we have
00:11discussed these topics mean median mode and range I hope you have understood
00:16these topics well if not I request please go through the previous video
00:21uploaded by me and then watch this video till the end your all concepts regarding
00:26data handling will be clear and one last thing if you have not liked and
00:31subscribed to the channel please do it right now I'm going to continue with the
00:36first exercise of data handling exercise 3.1 NCRT class 7 so you can have a look
00:44at the screen first question is just an activity based questions which you can
00:49do with your friends in your family you have to find the range of the height of
00:54any 10 people it is mentioned here in your class if you wish to do it in your
01:00class you can do otherwise you can do this activity in your family also so
01:05this activity based question I'm leaving for you I'm starting with question
01:09number two it says organize the following marks in a class assessment in
01:15a tabular form you have to make a table and then you need to answer these
01:20questions when we are arranging these smaller numbers in the table it is
01:25generally a tally table I hope everyone knows how to represent a number in the
01:30form of tally I'll just give you a quick recap if I have to write the number one
01:36it is just one vertical line if I need to write to two vertical lines for three
01:43it is three vertical lines for four it is 1 2 3 & 4 change starts at 5 it is 1
01:532 3 4 and a slanting line okay and the slanting line cutting all these 4 this
02:00is 5 so we generally use tally table when the numbers given are very small
02:05for example I need to write 6 what is 6 then it is 5 plus 1 so 1 number 1
02:12symbol for 5 this one and 6 if I need to make it 7 1 2 3 4 5 6 7 if I need to
02:23write 10 5 has to be repeated 2 times 1 2 3 4 5 1 2 3 4 5 I hope now it is
02:32understood how to represent the smaller numbers in form of tally so the format
02:38of tally table is it should have three vertical columns I suggest when you are
02:44making a table do not make a closed table once the observations are done we
02:50can close it later on it will make our task easier so what you're supposed to
02:54do use your ruler and a pencil and draw a table like this an open table I have
03:03drawn three lines like this now one for writing the title of the columns and
03:11then three equal columns like this three columns we have made question number two
03:18we are doing so what is all these numbers representing these are the marks
03:24so you have to give it the heading marks what we are writing here it is marks
03:30middle column always represents the tally marks that means the symbol to be
03:37given for the frequency we'll just discuss in a while and the last column
03:42is for frequency what is the meaning of frequency it means how many times a
03:49particular number is repeated in a data the set of observations right for
03:54example we are having a 4 here so we just need to calculate how many times
03:594 is repeated here that is the frequency and the tally we make for
04:04frequency only not for the data in the first column for the third column so
04:11whatever number you are going to get in the third column you are going to make
04:15tally marks for that third column so what title will it be getting it is
04:21frequency frequency means how many times an observation is repeated now
04:28have a look here what is the smallest value of the mark here it is 1 and what
04:35is the greatest value here that is 9 so we have to write the numbers 1 to 9 here
04:411 2 3 4 5 6 7 8 and 9 ok you have to get the numbers till 9 here after that you
04:53need to write total once it is done you have to write total here let me just
04:59extend this a little more that's what I said that you have to close this table
05:03later on we have to continue right now these lines are already being made for
05:10you quickly till the time I'm making the format of the table I request please
05:15found the frequency of each number that means how many times 1 2 3 4 5 6 7 8 9 is
05:23repeated in this particular data quickly just start making it it is quite
05:33an easier one no scope of confusion should be there it is very very scoring
05:38topic okay let me just change the color so that you make it okay number 1 we can
05:46see here 1 is repeated only one time so I'll just write the frequency 1 here
05:51what I used to do I always just cross the number once I have used it so that
05:58it gives us the confirmation that we have included that number already so 1
06:03is repeated 1 times frequency is 1 how many times 2 is repeated it is 1 here
06:09and 1 here it is repeated 2 times right to how many times 3 1 it is repeated
06:19only once we'll write 1 here how many times 4 1 2 3 4 is repeated 3 times now
06:29how many times 5 is repeated 1 2 3 4 and 5 5 is repeated 5 times what is the
06:41frequency of 6 1 2 3 & 4 6 is repeated 4 times for 7 it is 1 & 2 it is repeated
06:552 times how about 8 we can see here only 1 8 & 1 9 is here so you will give it a
07:02frequency 1 & 1 after writing all the frequency it is very very important to
07:09count what is the total frequency here the total frequency should be equal to
07:14the total of all these numbers that means how many observations are being
07:19given have a look it is 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 in
07:33total 20 observations are there so when you add all these frequency it should be
07:38equal to 20 if it is not that means you have made the error in the calculation
07:43and you need to reach it let us count 1 plus 2 3 4 5 6 7 8 9 10 11 12 12 plus 4
07:53is 16 plus 2 18 19 and 20 we got 20 it's not visible here I just put it here in
08:02the down in front of total you have to put 20 here the total frequency is 20
08:07you need not to make any telemark for the total for other numbers we have to
08:12make again I am repeating this telemarks to be made for frequency for the third
08:19column right so how will you represent 1 1 vertical bar 2 means 2 bar again we
08:26have 1 1 bar then we have 3 1 2 3 we have 5 1 2 3 4 5 1 2 3 4 1 2 1 and
08:371 right tally table is complete now let's write the answer of this question
08:42which number is highest which number is highest means which number has the
08:49highest frequency so please have a look subset but our frequency is the biggest
08:55frequency is 5 and for which number 5 is the frequency of 5 so answer of first
09:02part is 5 which number is lowest means which number has the least frequency the
09:09smallest numbers here are 1 1 1 and 1 or each other one kiss kiss my frequency a
09:17it is for 1 3 8 & 9 so 1 3 8 & 9 these 4 marks have the lowest frequency what is
09:31the range of the data data mirror data is not the frequency frequency just tell
09:36me a number is repeated how many times so whenever you are giving the answer of
09:41a range you have to choose the numbers from the given data and what's your data
09:47data is here range means greatest value minus lowest value so which is the
09:55greatest number here that is 9 and the lowest is 1 so what is the range it is
10:018 that's it finally you need to find the arithmetic mean arithmetic mean the sum
10:08of all the observations divided by the number of observations so let us add all
10:14the numbers and divided by we know how many total observations are there the
10:20total observations are 20 have a look total at 20 so whatever the sum will be
10:26coming you need to divide it by 20 let us count these numbers 6 plus 4 I
10:33request stop the video count it find the average and then reject your answer with
10:39the video 6 plus 4 is 10 10 plus 7 is 17 17 plus 3 is 20 plus 5 25 25 plus 5
10:52is 30 ok 4 plus 6 is 10 so 30 plus 10 is again 40 9 plus 1 50 9 plus 1 is 10 so
11:0340 and 10 is 50 6 and 4 is again 10 so we are getting 60 8 and 2 70 77 78 79
11:19then 5 and 5 89 was left out 89 plus 6 how much is that it is 95 and 95 plus
11:315 is 100 ok this is one of the best method of adding the numbers take the
11:37combination like 8 and 2 which gives you 10 5 and 5 gives you 10 3 and 7 gives
11:44you 10 6 and 4 gives you 10 so addition is commutative you can add the numbers
11:50in any order you get the same answer so I request practice the questions
11:54addition subtraction multiplication again and again to avoid the calculation
11:59errors so what did we get as the sum we are finding arithmetic mean so that is
12:05the sum of observation by the number of observation sum is 100 and total 20
12:12observations are there if we divide answer is 5 so your arithmetic mean is
12:175 moving on to question number 3 you have to find the mean of first 5 whole
12:25numbers finding the mean is exactly the same like we have done so what you're
12:32supposed to know which all are the first 5 whole numbers are we all aware of
12:38first 5 whole numbers the whole number start from 0 so first 5 whole numbers
12:44are 0 1 2 3 & 4 these are the first 5 whole numbers for finding the mean mean
12:52is what arithmetic mean average you need to find the sum and divided by how
12:58many numbers are there 1 2 3 4 5 question says the mean of first 5 whole
13:04number so the sum has to be divided by 5 4 plus 3 7 8 9 10 10 plus 0 is 10 so
13:14what is 10 divided by 5 your answer is 2 great answer of question number 3 is 2
13:21question number 4 is exactly the same so the questions where exact same
13:27formulas will be applied and just the calculations need to be done I expect
13:32you all to do it yourself I will just explain how the question to be done so
13:37a cricketer scores the following runs in the 8 innings 8 innings means 8
13:42matches the person has played and these are the scores you have to find the mean
13:47score what does mean exactly the same like we have done in question number 4
13:51question number 2 fourth part and third you need to add all these numbers and
13:57you have to divide them by how many observations are there 8 so take the sum
14:02of the numbers and divide by 8 without doing any calculation error and that
14:08will be your answer okay can we move to the next question now I expect you all
14:13to do it yourself moving on to the next part now question number 5 now says it
14:19is the data of three players player a player B and player C and the scores
14:27they have scored in four game game 1 2 3 & 4 but one thing you have to mind here
14:34player C has not played game 3 okay he has not played the game player B has
14:43played all the games but he has 4 0 in one game please understand if there is a
14:49person a okay 4 matches to be played he has played this this this and this one
14:55is not played whichever matches not played that means it's a 0 here so how
15:00many matches has he played 3 so you have to find the sum and it has to be
15:06divided by 3 not by 4 why because he has not played this much if he has played
15:15and then got a 0 you have to divide by 4 like in Deepak he has played all the
15:21matches whose car performance is not good that that are absolutely fine that
15:25he got a 0 but he has played okay so have a look at question number 5 first
15:30part find the mean to determine A's average number of points average
15:36question how to find the average of A you have to add all the numbers and
15:43divide by 4 1 2 3 & 4 I mind you whenever you are doing the questions for
15:49average mean median mode first of all you need to write the formula and after
15:55that only will show the calculation so average of A is you have to write the
16:01sum of the scores divided by the number of matches played what is the sum 14
16:08plus 16 it is 30 plus 10 40 plus 10 50 50 divided by 4 what is that equal to
16:1712.5 this is the average of A second part says if I have to find the mean of
16:24C will I divide by 3 or 4 and why in C part he has played 1 2 & 3
16:32matches this one is not played so will you divide by 3 or 4 you will write we
16:38will divide by 3 because he has played only three matches great next one B has
16:47played in all the four games how will you find the mean if he has played all
16:52the four then the sum has to be divided by 4 I'll just write it here average
16:57score of B is the sum of the scores divided by the number of matches what is
17:04the sum of these numbers 6 plus 4 is 10 10 plus is 18 and how many matches has
17:11he played 4 I have to consider the 0 he has played this much so 18 divided by
17:184 2 into 9 is 18 2 into 2 is 4 and 9 divided by 2 is what that is 4.5
17:26question number 4 says who is the best performer how do I know I know the
17:31average of A I know the average of B but I do not know the average of C so for
17:36answering this question I need to find the average of C correct 8 and 11 it is
17:4519 19 plus 10 is 29 29 plus 3 is it is 32 it has to be divided by 3 matches to
17:56be played it is 32 divided by 3 have a look here how do we divide 3 into 1 is
18:043 difference is 0 and 2 gone down I cannot take it further 32 means 32.0 to
18:12continue the division I need one more digit because 0 2 is less than 3
18:17whenever we need one more digit we need to put a 0 up okay that means we are not
18:25able to do 3 into 0 is 0 again the difference is 2 now this 0 can come down
18:32how but decimal is bothering put decimal in the question is for answer may be
18:380 will go down 3 into 6 is 18 difference 2 and again it will continue
18:46so you can take it round off as either 10.66 10.67 or 10.6 whichever you can
18:54take all are correct so which is the greatest number here is it 12.5 4.5 or
19:0110.6 easily we can make out average of A is greatest so A is the best
19:08performer right question number 6 now the marks out of 100 obtained by a group
19:17of students in science test are okay out of 100 it is the marks in a test it is
19:24given now what we are supposed to know highest and the lowest marks which is
19:29the highest mark here these two marks are also there please don't overlook so
19:34the highest now marks we can see it is 95 so highest is 95 lowest is we can see
19:42here only one mark is there in 30s so lowest is 39 you have to find the range
19:49of the mark how do we find range it is highest minus lowest so 95 minus 39 15
19:59minus 9 is what that is 6 we have taken one carry 8 minus 5 8 minus 3 is what it
20:07is 5 so answer is 56 that is the range you have to find the mean marks obtained
20:14by the group mean what does mean it is average we have already done several
20:19questions for average so I will just tell you how it has to be done average
20:25you need to add all the given numbers and divide by check it yourself you'll
20:31divide by what have a look how many observations are there 1 2 3 4 5 6 7 8
20:399 10 so whatever is the sum you need to divide it by 10 okay so please calculate
20:46what is the sum of all the numbers and divide by 10 that will be your mean
20:52question number seven exactly similar this is the enrollment means total
20:58number of admission in six consecutive years in a school consecutive means one
21:04after the other first year second year third year four five and six so in
21:09different consecutive years how many students have taken admission in the
21:13school it is being given again you have to find the mean mean means add all the
21:19numbers and divide by how many numbers are given six so you need to add the
21:24numbers and divide it by six so much of calculation to be done with a lot of
21:30accuracy Daniel only you will be able to do that right I hope you are able to
21:36understand this concept of finding the range mean arithmetic mean they are the
21:42same thing okay please like and subscribe and please follow the channel
21:48we'll continue with the next exercise in the next video thank you so much for
21:53watching take care