Aptitude Day 159

Problems on Average:

1. The average annual income of certain agricultural workers is S and that of other workers is N. The number of agricultural workers is 10 times that of other workers. Then the average monthly income of all the workers is:

Solution:

                The number of other workers = x.

                The number of agricultural workers = 10x.

                 Average = Sum of observations/ Number of observations

                                 = [(S(10x)+T(x))] / (10x+x)

                                 = x[10S+T]/11x

                                 = (10S+T)/11.

2. A family consists of grandparents, parents and 3 grandchildren. The average of the grandparents is  70 years, that of the parents is 40 years and that of the grandchildren is 8 years. What’s the average of the family?

Solution:

                 Average = [ 70(2) + 40(2) + 8(3) ] / [2 + 2 + 3]

                                 = 244/7

                                 = 34 (6/7).