statistics
posted by shweta .
The mean weight of 40 students is 50 kg. One of the student leave and is replaced by another student which reduces the mean weight of the class by 0.5 kg. If the weight of the student who left is 65kg, what is the weight of the student who joined the class.

Mean = Σx/n
50 = Σx/40
Σx = 2000
49.5 = (200065+x)/40
Solve for x.