Aptitude Day 150

Problems on Average:

1. Find the average of first 20 natural numbers.

Solution:

                Sum of 1^st 20 natural numbers = n(n+1)/2 = 20(21)/2 = 210.

             

                Average = Sum of observations/ Number of observations

                              = 210/20

                              = 10.5.

2. Find the average of first 10 multiples of 5.

Solution:

                Sum of 1^st 10 multiples of 5= 5 [n(n+1)/2] = 5[10(11)/2] = 275.

             

                Average = Sum of observations/ Number of observations

                              = 275/10

                              = 27.5.