The average weight of some students in a class was 62.5 kg. When 12 students, whose average weight was 66 kg, joined the class, then the average weight of all the students increased by 0.7 kg. The number of students in the class initially was?

42 48 60 65

48

Increased average = 62.5 + 0.7 = 63.2 Now using allegation: