13 thoughts on “Weighted Averages – 2

    • Vishal, we got the ratio of mixing of the original (milk mixture) to the new (water) as 4 : 1. Now the original is known to be 60 litres, hence 1/4 of that = 15 litres of water need to be added.


  1. Pingback: DS – Weighted Averages | CAT-holics

  2. sir in the last question, why are we taking 0 lts water what is the reason without understanding how can apply the logic to other problems?

  3. In second question, we would have taken 1:13, then in equation x+2=35-26 , taking 13 instead of 26 would affect the answer. How can we assume, we need to take 2:26 and not 1:13?

  4. Salute ‘J’ for these awesome basics testing questions.

    Q2: I thought I would spread this other idea which is specific to age related problems.

    Given that 35 years old teacher contributes 2 years to the average age of the class.

    Let us assume ‘x’ to be average age of the 13 students in the class. Now, when teacher’s age gets added to the total, it contributes 2 years to everyone’s age , i.e. ‘x’.

    So, 13 + 1 = 14, all 14 people have been given 2 years from the age of teacher in addition to their average age – ‘x’. So, now all 14 people in the group have an average age of (x + 2).

    So, 14 * 2 = 28. Now, we have 28 years from the age of teacher being redistributed to all 14 people having age – ‘x’. So, what is left of 35 after subtracting 28 is 7 years, which is the actual average age of the group of 14 people.


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