Quantitative Aptitude Questions and Answers On Average
11. The average age of 11 daughters of a family is 12yrs. Average age of the daughters together with their
parents is 27yrs. If mother is 14yrs younger than father. Then find the father's age.
Explanation: Total age of 11 daughters of a family = 11*12 = 132
father age = 14 +mother age
total age of the family
(11 daughters + father + mother) is,
132+mother +14+ mother = 27 * 13
mother = 102.5
father age = 14+102.5 =116.5years
12. The average height of a batch is 344 cm. 16more students with an average height of 320 cm joined the
batch therefore decreasing the average height of the batch by 12 cm. Find the total strength of the batch?
Explanation: let the initial strength of the batch be X
total height of the batch initially = 344X
total height of 16 new students = 320 * 16 = 5120 cm
Then, the average height of X+ 16students = 332
332 = [5120 + 344 X]/ [X + 16]
X= 16 students
13. In an competitive examination, the average was found to be 72 marks. After detecting the errors the
marks of 94 candidates had to be charged from 90 to 66 each, and the average is reduced to 64 marks. Find
the total number of candidates who took the exam?
Explanation: let the number of candidates be A
total marks of candidates = 72A
after detecting error the change of marks for one candidate = 90 - 66 = 24 marks
change of marks for 94 candidates = 94*24 =2256
after detecting error of N candidates = 64A
then, 72A- 2256= 64A ,
14. The batting average of runs of a cricket player of 30 innings was 96. How many runs must he make in his
next innings so as to increase his average of runs by 12?
Explanation: Given that the total average runs of a cricket player (30 innings) = 96
After 31 innings = 108
Required number of runs = (108 * 31 – (96 *30)
=3348 – 2880
15. The average weight of M,N and O is 168 kg. If P joins the group, the average weight of the group
becomes 160 kg. If another man Q who weighs 6kg more than P replaces M, then the average of N,O,P and
Qbecomes158 kg. What is the weight of M?
Explanation: M+N+O =168 * 3 =504
P=136 kg and Q =142 kg
N+O+P+Q =158*4 =632
N+O+P =632-142 =490 ---->(2)
from 1 & 2,
16. The mean of 8 article was found to be 15. On rechecking, it was found that two article were wrongly taken
as 11 and 9 instead of 16 and 14 respectively. Find the correct mean.
Explanation: Calculated mean of 8 articles = 15
Incorrect sum of these 8 articles = (15*8) = 120.
Correct sum of these 8 articles
= (incorrect sum) - (sum of incorrect articles) + (sum of actual articles)
= [120 - (20) + (30)]
Therefore, correct mean = 130/8 = 16.25
Hence, the correct mean is 16.25
17. Gowshik is going to market from his home by bike at a speed of 20kmph. While he comes back to his
home with a speed of X kmph, what should be the value of x so that his average speed is 24kmph ?
Explanation: Let speed be X
Average speed =2xy/(x+y)
18. The average marks of a class of 90 students is 126. Out Of them, 4 scores zero, first 60 students scored
an average of 116, next 24 scored an average of 118. What is the mark obtained by the remaining student in
Explanation: According to the question,
19. When the average age of a father, mother and their son was 90 years, the son got married and a child
was born just 6 year after the marriage when child turned 14 years the average age of the family is 80yrs.
Find the age of daughter - in - law at present?
Explanation: Total age of father, mother and son at the time of son's marriage = 90*3 =270
present age of family father, mother, son, daughter-in-law, child = (father, mother, son age at the time of
marriage) + daughter-in-law present age + child present age
= (270+60)+ daughter-in-law present age + 14 = 80*5 =400
daughter-in-law present age= 400-344 = 56yrs
20. The average age of the men in a team is 76 years and that of the women is 75 years. The average age for the whole team is
Explanation: Clearly to find the average, we ought to number of men, women or total persons in the class, neither of which has been given. So the data provided is inadequate