Multiple choice

In a group of persons, the average weight is 60 kg. If the average weight of males and females taken separately is 80 kg and 50 kg respectively, find the ratio of the number of males to that of females.

  1. 2 : 3

  2. 3 : 2

  3. 2 : 1

  4. 1 : 2
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D Correct answer
Explanation

Using the allegation method: Mean weight 60, Male 80, Female 50. Difference for males = 60-50 = 10. Difference for females = 80-60 = 20. Ratio of males to females = 10:20 = 1:2.

AI explanation

Using the method of alligation, the ratio of males to females is proportional to the difference between the female average and the combined average, to the difference between the combined average and the male average. This gives the ratio as 60 minus 50 to 80 minus 60, which is 10 to 20. Therefore, the ratio of males to females is 1 to 2.

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