the mean weight of 35 students of a class is 60 kg if the mean weight of first 18 students 64 kg and the mean weight of the last 18 students is 55 kg find the weight of the 18th student
Answers
mean weight of 35 students =60 kg
total weight of 35 students =60*35 kg
=2100 kg
mean weight of first 18 students = 64kg
total weight of first 18 students =64*18 kg
=1152 kg
mean weight of the last 18 students =55 kg
total weight of last 18 students =55*18 kg
=990 kg
total weight of first 18 students+total weight of last 18 students=1152+990
=2142 kg
total weight of first 18 students+total weight of last 18 students contains the weight of the 18th student twice since in both first 18 and last 18 the 18th student is common
therefore
weight of 18th student= total weight of first 18 students+total weight of last 18 students-total weight of 35 students =2142-2100
=42
the 18th student weighs 42 kg