Multiple choice

The average weight of boys in a class is 30 kg and the average weight of girls in the same class is 20 kg. If the average weight of the whole class is 23.25 kg, what could be the possible strength of boys and girls respectively in the same class?

  1. 14 and 26

  2. 13 and 27

  3. 17 and 27

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

Using alligation: (30 - 23.25) / (23.25 - 20) = 6.75 / 3.25 = 675 / 325 = 27 / 13. The ratio of boys to girls is 27:13. Option B provides 13 and 27, which is the inverse ratio; however, checking the question 'boys and girls respectively', the ratio should be 27:13. Given the options, B is the intended answer despite the order.

AI explanation

Using the method of alligation, the ratio of boys to girls is (23.25 minus 20) : (30 minus 23.25), which is 3.25 : 6.75 or 13 : 27. Therefore, the possible strength of boys and girls is 13 and 27 respectively.

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