Question 53

In a class with a certain number of students, if one student weighing 50 kg is added then the average weight of the class increases by 1 kg. If one more student weighing 50 kg is added then the average weight of the class increases by 1kg. If one more student weighing 50kg is added then the average weight of the class increase by 1.5 kg over the original average. What is the original average weight (in kg) of the class. ?

Solution

Let the number of students in class be n and average weight be A kgs and S be the sum of ages of all the students.

So, ΣS/n = A

ΣS + 50/n+1 = A + 1

ΣS + 50 + 50/n+2 = A + 2

ΣS + 50 + 50 + 50/n+3 = A + 3.5

On solving, the above equations, we get

A = 47

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