(a) Total weight of seven students in team A = 7 x 66 = 462 kg Total weight of five students in team B = 5 x 64 = 320 kg Total weight of the students who leave the group = 3x62 = 186 kg Average weight of students of teams A and B
462+320
12
= 65.1 = 65 kg According to the question, Average weight of nine students =
462+320−186
9
=
596
9
= 66.2 = 66 kg So, the average of combined team increases by 1 kg.