The average marks of 42 students in an examination, was 64. Later it was found that the marks of three students were misread as 72, 58 and 44 instead of the actual marks 64, 42 and 26 respectively. What is the correct average marks?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 63
Average = Sum of all numbers/Total numbers
The average marks of 42 students in an examination was 64
so sum of 42 students in an examination = 42 × 64 = 2688
Later it was found that the marks of three students were misread as 72, 58 and 44 instead of the actual marks 64, 42 and 26 respectively
Net increase/decrease = (72 + 58 + 44) - (64 + 42 + 26) = 174 - 132 = 42 decrease
Actual sum = 2688 - 42 = 2646
Correct average = 2646/42 = 63.