Multiple choice

Mean weight of 21 students of a group is 40 kg. If the mean weight of first 10 students is 42 kg and that of last 10 students is 38 kg, then the weight of 11 the student is

  1. 20 kg

  2. 40 kg

  3. 30 kg

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Sum of 21 = 21*40 = 840. Sum of first 10 = 10*42 = 420. Sum of last 10 = 10*38 = 380. 11th student = 840 - (420 + 380) = 840 - 800 = 40.

AI explanation

The total weight of all 21 students is 21 multiplied by 40, which equals 840. The total weight of the first 10 students is 10 multiplied by 42 (420), and the total weight of the last 10 students is 10 multiplied by 38 (380). The sum of these two groups is 420 plus 380, giving 800. The weight of the 11th student is the overall total minus this combined group weight, so 840 minus 800 equals 40 kg.

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