Averages
Practice Questions on Averages
Q8) Average of 'n' elements in a group is 12. Each of these 'n' elements is multiplied by 'k'. Find the new average. If each number in the group is multiplied by 'k', then average of the group also multiplied by 'k'. Hence, option 3. Q9) Find the average of first k natural numbers.  Sum of first k natural numbers  Average of first k natural numbers  Hence, option 1. Q10) In Aman’s opinion his weight is greater than 66 Kg but less than 73 Kg. His sister does not agree with him and she thinks that Aman’s weight is greater than 62 Kg but less than 70 Kg. His mother’s view is that his weight cannot be greater than 69 Kg. His father is of the view that his weight cannot be less than 66 Kgs. If all of them are correct in their estimation, what is the average of different possible weights of Aman? 1) 67 Kg 2) 69 Kg 3) 68 Kg 4) Data Insufficient Say weight of Aman is y Kg. According to Aman, 66 < y < 73 According to Aman’s sister, 62 < y < 70 According to Aman’s mother, y ≤ 69 According to Aman’s father, y ≥ 69 Possible values of y are 67, 68, 69. ∴ Required average =(67 + 68 + 69)/3 = 68 Kg Hence, option 4. Q11) The average of the test scores of a class of ‘m’ students is 70 and that of ‘n’ students is 91. When the scores of both the classes are combined, the average is 80. What is n/m? 1) 11/10 2) 13/10 3) 10/11 4) 10/13 70m + 91n = 80(m + n) 11n = 10m n/m = 10/11 Hence, option 1. Q12) The mean weight of 150 students in a class is 60 Kg. The mean weight of the boys is 70 Kg and that of the girls is 55 Kg. What is the number of boys in the class? 1) 50 2) 60 3) 75 4) 100 Number of boys in the class = b 150*60 = 70b + 55(150 - b) 15b = 5*150 b = 50 Hence, option 1. Q13) The average age of 3 boys is 15 yr. If the ratio of their ages is 3:5:7, what is the age of the oldest boy? 1) 7 yr 2) 14 yr 3) 20 yr 4) 21 yr Sum of the ages = 15*3 = 45 Age of the oldest boy = 7*45/(3+5+7) = 21 yr Hence, option 4. |