The average marks obtained by a class in an examination were calculated as 30.8. However, the marks of one student were entered incorrectly as 24 instead of 42. After correcting the marks, the average becomes 31.4. How many students does the class have?
Options:
(A) 25
(B) 28
(C) 30
(D) 32
Official Answer Key:
C
Step-by-Step Solution & Explanation
Let n = number of students. Correct sum = 30.8n + (42−24) = 30.8n + 18. New average: 31.4 = (30.8n+18)/n ⇒ 0.6n = 18 ⇒ n = 30.
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