Multiple choice

The average weight of the people in a Yoga class is 65 kg and the average weight of people in another class is 70 kg. Find the ratio of number of people in first class to that in second class, if the average weight of people in both the classes is 67 kg.

  1. 1 : 2

  2. 3 : 2

  3. 4 : 5

  4. 4 : 3
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Use alligation: (70 - 67) / (67 - 65) = 3 / 2.

AI explanation

Using the method of alligation, the overall average weight is 67 kg. The differences between the overall average and the averages of the two individual classes are 2 kg for the first class (67 - 65) and 3 kg for the second class (70 - 67). The ratio of the number of people is the inverse of these differences, which is 3:2. Therefore, the ratio of the number of people in the first class to the second class is 3:2.

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