Question

In a class of 100 students, the mean marks obtained in a subject is 30 and in another class of 50 students the mean marks obtained in the same subject is 60. The mean marks obtained by the students of two
classes taken together is :
(a) 40
(b) 45
(c) 48
(d) 50​

Answer 1

Answer:

(a) 40

Step-by-step explanation:

Mean of 100 students =30

Mean of 50 students =60

Mean of 150 students = (100∗30+50∗60)/150

= (3000+3000)/150

= 6000/150

=40

Hence, mean marks obtained is 40.

Answer 2

Case (i)

Number of students = 100

Mean marks = 60

So , total sum of marks of 100 students = 30 × 100

= 3000

Case (ii)

Number of students = 50

Mean marks = 60

So , total sum of marks of 60 students

= 60 × 50

= 3000

Now ,

Mean / Average marks of two classes

$= \frac{3000 + 3000}{100 + 50}$

$= \cancel\frac{6000} {150} ^{40}$

$\sf = 40 \: marks$

Therefore , average / mean marks of two classes = 40.

____________________________

$\huge \underline\color{Black} \sf{Extra \: जानकारी}$

$\small\sf{⇝ Average \: and \: mean \: are \: synonyms \: of} \\ \small \sf {each \: other \: .}$

$\small\sf{⇝ Average/mean \: = \frac{sum \: of \: observation}{number \: of \: observation}}$