Examples(Set 3) - Average

11. A family consists of two grandparents, two parents and three grandchildren. The average age of the grandparents is 67 years, that of the parents is 35 years and that of the grandchildren is 6 years. What is the average age of the family in years?
A.222/7
B.221/7
C.220/7
D.219/7

Answer: Option A

Explanation:
Total age of grandparents = 67 × 2
Total age of parents = 35 × 2
Total age of grandchildren = 6 × 3
Total age of all persons = 67 × 2 + 35 × 2 + 6 × 3 = 222
Total number of persons = 2 + 2 + 3 = 7 = 7
Average age of the family = 222/ 7






12. The average weight of Advay, Bharat and Chiku is 45 kg. If the average weight of Advay and Bharat be 40 kg and that of Bharat and Chiku be 43 kg, what is the weight of Bharat?
A. 28.5 kg
B. 31 kg
C. 32 kg
D. 30.5 kg

Answer: Option B

Explanation:
Total weight of Advay+Bharat+Chiku = 45 × 3 = 135
Total weight of Advay+Bharat = 40 × 2 = 80
Therefore, weight of Chiku = 135 − 80 = 55
Total weight of Bharat+Chiku = 43 × 2 = 86
Hence weight of Bharat = 86 − 55 = 31






13. If the average marks of three batches of 55 , 60 and 45 students respectively is 50 , 55 , 60 , what is the average marks of all the students?
A. 50
B. 51.33
C. 53.23
D. 54.68

Answer: Option D

Explanation:
Required average = (55 × 50 + 60 × 55 + 45 × 60)/ (55 + 60 + 45)
= 54.68






14. The average age of husband, wife and their child 3 years ago was 27 years and that of wife and the child 5 years ago was 20 years. What is the present age of the husband?
A. 28
B. 30
C. 40
D. 32

Answer: Option C

Explanation:
average age of husband ,wife and child 3 years ago=27
sum of ages of husband ,wife and child 3 years ago=27x3
present sum of ages of husband ,wife and child =(27+3)x3=90

average age of wife and child 5 years ago=20
sum of ages of wife and child 5 years ago=20x2
present sum of ages of wife and child =(20+5)x2=50

present sum of ages of husband=90-50
=40






15. The average weight of 8 persons increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg. What is the weight of the new person?
A. 50 kg
B. 85 kg
C. 80 kg
D. 75 kg

Answer: Option B

Explanation:
Let weight of new person be x
Total increase in weight = 8 × 2.5 = 20
⇒ x − 65 = 20
⇒ x = 85






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