Question

The mean weight of 25 students of a class is 52 kg. If the mean weight of the first 13 students of the class is 48 kg and that of the last 13 students is 55 kg, find the weight of the 13th student.

Answer 1

ANSWER:
Mean weight of 25 students = 52 kg
Sum of the weights of 25 students = (52×25) kg = 1300 kgMean weight of the first 13 students = 48 kg
Sum of the weights of the first 13 students = (48×13) kg = 624 kg
Mean weight of the last 13 students = 55 kg
Sum of the weights of the last 13 students = (55×13) kg =715 kg
Weight of the 13th student = (Sum of the weights of the first 13 students + Sum of the weights of the last 13
students) - Sum of the weights of 25 students
= [(624+715)-1300] kg
= 39 kg
Therefore, the weight of the 13th student is 39 kg.