# Aptitude questions – Averages – Set 3

Q.1) An office assistant boy counted the chairs in 12 class rooms and found  the average of chairs in a class room to be 90.  Latter he found that he had wrongly counted the chairs  in three class rooms  as 74, 65 and 85. Actually correct number is 83, 86 and 91. What is the new average of chairs in a class room?

a) 84

b) 87

c) 96

d) 93

e) None of these

d

((12×90)-74+83-65+86-85+91)/12=93

Q.2) The average marks obtained by a student in physics, chemistry, Biology and Maths together is 45% above the average marks obtained in chemistry and Biology together. How many marks exceeds by average of chemistry and Biology together and sum of the physics and maths together?

a) 65

b) 87

d) 78

e) None of these

c

There is no other information about the marks in any one of the subject, the data given is insufficient to answer the question.

Q.3)  13 years ago the average age of a family which includes father, mother, daughter and son was 35 years. 7 years ago the average age of father, mother and son was 48 years, then find out the daughter’s age  after 9 years.

a) 21 yrs

b) 25 yrs

c) 28 yrs

d) 36 yrs

e) None of these

d

Total age of a family father, mother, daughter and son=(35×4)+52=192 yrs

Total age of father, mother and son at present=(48×3)+21=165 yrs

The present age of son=192-165=27

Son’s age after 9 years=27+9=36

Q.4) In an elementary school, the average age of 9 kids is 9 years. If the sum of 1st two kids age is 12 yrs, the average of next 2 kids is  years, and the sum of   the ages of next 2 kids is 5 years and the eighth and ninth kids ages exceeded the Seventh kids by 2 years and 4 years respectively, then the eighth kids age is, (Approximately)

a) 13 years

b) 16 years

c) 10 years

d) 14 years

e) 12 years

b

Sum of age of 9 kids=9×9=81 yrs

sum of 1st 2 kids=12 yrs

Sum of next 2 kids=2×15/2=15 yrs

Sum of next 2 kids=5 yrs

Seventh kids age=X

Eight kids=X+2

Ninth kids=x+4

12+15+5+x+x+2+x+4=81

3x=43

x=14 yrs

Eight kids age is=x+2=14+2=16 years

Q.5) The sum of ages of 5 members are father, mother, son and 2 daughters of a family. 4 years ago was 80 years. At present, when one daughter has been married off and replaced by daughter-in-law. Now sum of family members age is 178 years. If no other change in the family Structure, then what is the average age of married daughter and daughter-in – law’s  age?

a) 19

b) 21

c) Cannot be determined

d) 11

e) None of these

c

The given data is insufficient to answer the question.

Q.6) A box contains 120 books. Out of which there are 35 novel books, 40 Banking books, 30 Drawing books and remaining books are TNPSC books. The average number of 120 books containing 700 pages and the average number of novel books contains 120 pages.  Sum of the pages in Banking book is150 pages more than the number sum of the  pages of novel book. Total number of pages in Drawing book is 10% of total number of banking books, find the average number of pages containing the TNPSC book?

a) 6350

b) 4500

c) 7704

d) 5001

e) None of these

d

Total pages containing a 120 books=120×700=84000

Total pages containing novel books=35×120=4200

Total number of pages of Banking book=4200+150=4350

Total pages of Drawing book=4350×10/100=435

Number of pages containing TNPSC book=84000-8985=75015

Average number of pages containing the TNPSC book=75015/15=5001

Q.7) The average weight of 55 girls in a Biology department is 80% of the number of girls in the same department and the average weight of a group of 18 girls present in the department is 42 kg and the average weight of another 18 girls in the class is 40 kg, What is the average weight of the remaining girls in the department? (Approximately)

a) 47 kg

b) 43 kg

c) 50 kg

d) 48 kg

e) 52 kg

c

Average weight of 55 girls=55×80/100=44 kg

According to the question,

55×44=18×42+18×40+19×x

2420=756+720+19x

x=944/19=50 kg

Q.8) In a exhibition 20% of the students went for science exhibition and the remaining students went for social exhibition. The number of students went for science exhibition is 250 and they had the total number of 2500 boxes. And the students went for social exhibition had the boxes which are 50% more than that of the number of students went for social exhibition. Find the average boxes had by total students.

a) 2.5

b) 3.2

c) 5

d) 7

e) 3

b

The number of student went for science exhibition (20%) = 250

100%=x

x=(250×100)/20=1250

Total student x=1250

The number of student went for social exhibition = 80/100×1250=1000

The number of boxes, the students went for social exhibition had  = 150/100×1000=1500

Total number of box=2500+1500=4000

Average=4000/1250=3.2

Q.9) Out of 6 numbers, the average of the first five numbers is 25 and that of last 5 numbers is 27. If the first number is 28, then the last number is,

a) 29

b) 41

c) 38

d) 37

e) None of these

c

A+B+C+D+E=25×5=125

B+C+D+E+F=27×5=135

B+C+D+E=125-A

B+C+D+E=125-28=97

97+F=135

F=135 -97=38

Q.10) The average age of mother and daughter is 28 years. The difference between the present age of mother and daughter is  22 years. What will be ratio of their ages after 3 years?

a) 11 : 21

b) 21 : 10

c) 15 : 17

d) 23 : 19

e) 19 : 22

b

Let mother and daughter age be X and Y respectively,

Sum of mother and daughter^’ sage=28×2=56

x+y=56——-(I)

Difference between Mother and daughter age=22

x-y=22——-(II)

Solve the equation I and II, and

we get, Mother age (x)=39

Daughter age (y)=17

Ratio of after three years= (39+3) : (17+3)

42 : 20=21 : 10