Aptitude Day 179

Answers of Day 178: 

1.       23(13/14) kg.

2.        26 years.

Problems on Average:

1. 5 years ago, the average age of the family of 3 members was 20 years. 2 children having been born (with age difference of 3 years), the present average age of the family is the same. The present age of the youngest child is:

Solution:

                  Sum = 20*3 = 60.

                  Present sum of the age of 3 members = 60+5(3) = 75.

       

                  The average remains the same after their birth too. Hence,

                   Sum = 20*5 = 100.

                   Let the present age of the youngest child be x and the age of the other child be x+3.

                   x + (x+3) = 100-75

                   2x = 25-3

                   x = 11 years.

2. The arithmetic mean of the scores of a group of students in a test was 40. The brightest 30% of them secured a mean score of 90 and the dullest 10% a mean score of 35. The mean score of remaining 60% is:

Solution:

                 (90*30)+(35*10)+(x*60) = 40*100

                  2700+350+60x = 4000

                  60x =4000-3050

                  x = 15.83 approximately.