Multiple choice

The average of marks of 45 students in a class is 40. The average of those who pass is 52 and those who fail is 16. How many students are failed?

  1. 15

  2. 30

  3. 25

  4. Data inadequate

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let f be the number of students who failed and p be those who passed. We have f + p = 45. Total marks = 45 × 40 = 1800. Also: 52p + 16f = 1800. Substituting p = 45 - f: 52(45 - f) + 16f = 1800, giving 2340 - 52f + 16f = 1800, so 2340 - 36f = 1800, therefore 36f = 540 and f = 15. The marked answer (A: 15) is correct.

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