Multiple choice

The average of marks obtained by $120$ candidates was $35$. If 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

  1. $120$
  2. $110$
  3. $100$
  4. $150$
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C Correct answer
Explanation

Let P be the number of passed candidates. Then 120 - P is the number of failed candidates. 39P + 15(120 - P) = 120 * 35. 39P + 1800 - 15P = 4200. 24P = 2400, so P = 100.

AI explanation

Let the number of passed candidates be p. The total marks of all candidates is 120 times 35 = 4200. Using the average formula, 39p + 15(120 minus p) = 4200, which simplifies to 24p = 2400, giving p = 100. The number of passed candidates is 100.

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