Multiple choice

There are 100 students in 3 class VI, VII and VIII of a School. The average weight of all the three class taking together is 42 kg. The average weight of VII and VIII is 43.75 kg and the average weight of VI is 35. The number of students in VI is

  1. 20

  2. 35

  3. 30

  4. 25

  5. 24
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A Correct answer
Explanation

Let students in VI = v. Total students = 100, so students in VII and VIII = 100 - v. Total weight = 100 × 42 = 4200 kg. Weight of VII + VIII = (100-v) × 43.75. Weight of VI = v × 35. So: v×35 + (100-v)×43.75 = 4200. This gives 35v + 4375 - 43.75v = 4200, so -8.75v = -175, giving v = 20.

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