Aptitude Day 154

Problems on Average:

1. The average of the first 6 prime numbers is:

Solution:

                 Average = Sum of observations/ Number of observations

                 Average = 2+3+5+7+11+13/6

                                 = 41/6

                                 = 6 (5/6).

2. A student was asked to find the arithmetic mean of the numbers 5, 7, 9, 11, 15, 17, 20 and x. He found the mean to be 12. What should be the number in place of x?

Solution:

                  Mean = 12           

                  12 = (5+7+9+11+15+17+20+x)/ 8

                  12 = 84+x/8

                    x = 12.