Question 56

The average of marks obtained by 120 candidates was 35. If the average of the passed candidates was 39 and that of the failed candidates was 15, then the number of those candidates who passed the examination, was

Solution

T = total students, P =passed, F = failed students

AVERAGE = SUM OF MARKS OF ALL STUDENTS/ NUMBER OF STUDENTS

A = 35 = ΣT/120

ΣT = ΣF + ΣP = 120*35 = 4200 ---(1)

and ΣP = 39*P, ΣF = 15*F [F = 120-P]

Putting values of ΣP and ΣF in equation 1, we get

4200 = 15(120-P) + 39P

4200 = 1800 - 15P + 39P

24P = 2400

P = 100 (passed students)

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