Multiple choice

There are 1600 students in a college, whose average weight is 50 kg. If average weight of boys is 54 kg. and average weight of girls is 38 kg. then find the number of girls in the school. एक स्कूल में 1600 छात्र हैं, जिनका औसत भार 50 किग्रा. है | यदि लड़कों का औसत भार 54 किग्रा. है और लड़कियों का औसत भार 38 किग्रा. है, तो लड़कियों की संख्या ज्ञात कीजिये |

  1. 400

  2. 800

  3. 1200

  4. 1000

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A Correct answer
Explanation

Using alligation method: Average 50 kg is between boys (54 kg) and girls (38 kg). The ratio of boys to girls is (50 - 38):(54 - 50) = 12:4 = 3:1. If 3 parts = 1200 boys, then 1 part = 400 girls. Alternatively: 54x + 38(1600 - x) = 50 × 1600. Solving gives x = 1200 boys, so girls = 400.