Question

The average of marks obtained by 120 candidates in a certain examination is 35. if the average score of passed candidates is 39 and that of the failed candidates is 15, what is the number of candidates who passed the examination?

Answer 1

Let x be the number of candidates who passed the exam and y be the number who failed

So,

x+ y = 120 ...............1)

Now,

Average = (Sum of all values)/ (Number of values taken)

So,

Total marks of students who failed= 15y

Total marks of students who passed= 39x

Now,

( 39x + 15y) /120 = 35

39x + 15y = 4200.......................2)

Multiplying equation 1) by 15 and then substracting from 2) we get

24x = 4200

x=2400/24

x = 10

Substituting x = 10 in equation 1)

10 + y =120

y = 110

Hence,

10 students passed and 110 students failed in the exam

Answer 2

Answer:

ans is X=100

y=20

Step-by-step explanation:

x be the number of candidate who passed

y be the number of candidate who failed

x+y=120-------(1)

15=total marks of who failed/y

15y= total marks who failed

similarly

39=total marks who passed/x

39x=total marks of who passed

(39x+15y/120)=35

39x+15y=4200--------(2)

multiply equation 1 by 15 and subtracting 1by 2

we get 24x =2400

x=100

and x+y=120

100+y=120

y=20

therefore the number of candidate who passed the examination is X=100