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Question

In a class of ‘x’ students, if a new student weighing 32 kg joins the class, then the average weight of the class increases by 1 kg. If the new student’s weight is 16 kg, then the average weight of the class decreases by 1 kg. Find ‘x’?

A 6 Correct Answer Incorrect Answer
B 7 Correct Answer Incorrect Answer
C 5 Correct Answer Incorrect Answer
D 8 Correct Answer Incorrect Answer
E 9 Correct Answer Incorrect Answer

Solution

Number of students in the class is x.
Let the Average weight of the class be y.
Total weight of the class = xy
If one student (32 kg) joins, comparing total weight of the class,
(xy+32)/(x+1) = (y+1)
x + y = 31 ------- (i)
If one student (16 kg) joins, comparing total weight of the class,
(xy + 16)/(x+1) = (y-1)
-x + y = 17 -------- (ii)
Solving the equations (i) & (ii) we get,
x = 7
Therefore the total number of students in a class is 7.

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