The average marks obtained by 100 candidates in an examination is 50. Find how many candidates have passed in the examination, if the average marks of candidates who passed is 70 and that of failed candidates is 20.
Choose the correct choice from the following:
A) 33
B) 77
C) 60
D) 29
E) 11

Rationale: explanation : let the number of students who passed the examination be x number of students failed = ( 100 - x ) total marks of students who have passed = 70 x total marks of 100 students = 100 * 50 = 5000 total marks of students who have failed = 20 ( 100 – x ) 20 ( 100 – x ) + 70 x = 5000 2000 – 20 x + 70 x = 5000 50 x = 3000 x = 60 answer : c
Answer: C