The average weight of a certain number of students in a class is 67.9 kg. If 4 new students having weights 69.5 kg, 69.3 kg, 73.5 kg and 68.5 kg join the class, then the average weight of all the students increase by 400 gms. The number of students in the class initially is?

19

Old avg. weight = 67.9

Average weights of new students = \(\frac{69.5 + 69.3 + 73.5 + 68.5}{4}\) = 70.2

New avg weight = 67.9 + .4 = 68.3