Aptitude Day 171

Problems on Average:

1. The average of 6 numbers is 57. The average of 1^st 2 numbers is 10(1/2) and the next 2 numbers is 5(1/2) and the 5^th one is 5 less than the 6^th one. Find the 6^th one.

Solution:

                 Let the 6^th number be x.

                 5^th number = x-5.

                10(1/2)(2) + 5(1/2)(2) + (x-5) + x = 57.

                21(2)/2 + 11(2)/2 + 2x-5 = 57

                32-5+2x =57

                x = 15.

2. If the arithmetic mean of 60 numbers is calculated, it’s 30. If each number is increased by 3, the mean of new numbers is:

Solution:

                 Sum of 60 numbers = 30*60 = 1800.

                 Increased sum = 3*60 = 180.

                Mean of new numbers = (1800+180)/60

                                                          = 1980/60

                                                          = 33.