Multiple choice

The average weight of 40 students is 35 kg. The average weight of first 25 is 30 kg. and last 16 is 42 kg. What is the weight of the 25th student? 40 छात्रों का औसत भार 35 किग्रा. है | प्रथम 25 का औसत भार 30 किग्रा. है और अन्तिम 16 का औसत भार 42 किग्रा. है | 25 वें छात्र का भार क्या है ?

  1. 20

  2. 24

  3. 22

  4. 26
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C Correct answer
Explanation

Total weight = 40 × 35 = 1400 kg. Sum of first 25 = 25 × 30 = 750 kg. Sum of last 16 = 16 × 42 = 672 kg. The 25th student is counted in both groups, so weight of 25th = 750 + 672 - 1400 = 22 kg. The double-counting of the 25th student lets us find their individual weight.

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