Question
The average weight of 30 students in a class is 60 kg.
When one student leaves and another joins, the average becomes 59.5 kg. The student who left had weight 72 kg. Find the weight of the new student.Solution
ATQ, Total weight of original 30 students = 30 × 60 = 1800 kg After change, total = 29 old + 1 new = 30 students, average 59.5 kg So new total weight = 30 × 59.5 = 1785 kg Weight of 29 remaining students = 1800 − 72 = 1728 kg Let new student’s weight = w. Then 1728 + w = 1785 w = 1785 − 1728 = 57 kg.
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