The average weight of a family of 4 members is 45 kg. The grandfather and the grandmother come to visit the family. Now the average weight of the 6 members of the family is 48 kg. Find the average weight of the grandparents (in kg).

54

Sum of weights of 4 family members = 4 x 45 = 180

Sum of weights of whole family = 6 x 48 = 288

Sum of weights of grandparents = 288 - 180 = 108

Average of weight of grandparents = 54 kg