Average

1. The average of all odd numbers upto 100 is:

51 48.5

50 49.2

Answer & Explanation

Answer: 50

Explanation: Sum of odd numbers upto 100

=1+3+5+7+...+95+97+99 =(1+99)+(3+97)+(5+95)+ . ..upto 25 pairs. =100+100+100+ ...(25times)=2500.

Average = 2500 / 50 = 50.

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2. The average of 50 numbers is 38. If two numbers, namely 45 and 55 are discarded, the average of the remaining numbers is :. [C.B.I. 1990]

36.5 37.5

37 37.52


Answer: 37.5

Explanation: Totalsumof48 numbers =[50*38 - (45+55)] = 1800.

Required average = 1800 / 48 = 37.5.

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3. The mean of 100 observations was calculated as 40. It was found later on that one of the observations was misread as 83 instead of 53. The correct mean is :. [C.B.I. 1993]

39 40.3

39.7 42.7


Answer: 39.7

Explanation: Correct sum = (40*100 + 53 - 83) = 3970.

Correct mean = 3970/100 = 39.7

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4. In a cricket eleven, the average of eleven players is 28 years. Out of these, the average ages of three groups of three players each are 25 years, 28 years and 30 years respectively. If in these groups, the captain and the youngest player are not included, and the captain is eleven years older than the youngest player, what is the age of the captain ?. [Hotel Managemen]

33 years 35 years

34 years 36 years


Answer: 35 years

Explanation: Let the age of youngest player be x.

Then, age of the captain = (x + 11).

3*25 + 3*28 + 3*30 + x + x + 11 = 11*28.

⇒ 75+84+90+2x+11=308 so 2x=48 so x=24.

Age of the captain=(x+11) = 35 years.

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5. The average weight of 6 men decreases by 3 kg when one of them weighing 80 kg is replaced by a new man. The weight of the new man . [LJ.D.C. Exam 19]

56 kg 62 kg

58 kg 76 kg


Answer: 62 kg

Explanation: Total weight decreased = (6*3) kg = 18 kg. Weight of new man = (80 - 18) kg = 62 kg.

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[10/15/2015 6:11:54 PM]

6. The average age of 40 student of a class is 15 year. When 10 new students are admitted, the average is increased by 0.2 years. The average age of new students is :. [AssistaDt Grade]

15.2 yrs16.2 yrs

16 yrs 16.4 yrs


Answer: 16 yrs

Explanation: Sum of ages of 10 new students = (50*15.2 - 40*15) = 160 years

. Average age of new students = 160/10 = 16 years.

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7. The average of Kanchans marks in 7 subjects is 75. His average in six subjects excluding Science is 72. How many marks did he get in Science? . [Bank P.O., 1993]

72 93

90 100


Answer: 93

Explanation: Marks in Science (7*75 - 6-72) = 93.

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8. The average age of 30 students of a class is 12 years. The average age of a group of 5 of the students is 10 years and that of another gfoup of 5 of them is 14 years. What is the average age oi the remaining students?. [Bank P.O. 1990]

8 years 12 years

10 years 14 years


Answer: 12 years

Explanation: Total age of 20 students = (30 * 12) - (5*10 + 5*14)= 240 years.

Required average = (240/20) = 12 years.

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9. Mukesh has twice as much money as Sohan and Sohan has 50% more money than what Pankaj has. If the average money with them is Rs 110, then Mukesh has :. [Assistant Grade]

Rs 55 Rs 90

Rs 60 Rs 180


Answer: Rs 180

Explanation: Let pankaj has Rs x

then sohan has 150% of Rs x = 150x/100 = Rs 3x/2

mukesh has 3x ⇒ x + (3x/2) + 3x = 110*3 ⇒ 11x/2 =110*3 ⇒ x= 60

mukesh has Rs 180

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10. The average of first five prime numbers is:. [Assistant Grade]

5.4 5.7

5.6 7.5


Answer: 5.6

Explanation: aveage = (2 + 3 +5 + 7 + 11)/5 = 5.6

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[10/15/2015 6:12:28 PM]

11. Out of four numbers, the average of first three is 16 and that of the last three is 15. If the last number is 18, the first number is

20 23

21 25


Answer: 21

Explanation: Sum of 2nd and 3rd number = (3*15 - 18) = 27.

First number = (3*16 - 27) = 21.

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12. The average weight of 3 men A, B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man F, whose weight is 3 kg more than that of D, replaces A then the average weight of B, C, D and E becomes 79 kg. The weight of A is:. [Bank P.O. 1989]

70 kg 75 kg

72 kg 80 kg


Answer: 75 kg

Explanation: A+B+C = (84x3) = 252kg, A+B+C+D=(80x4) = 320kg.

D = (320 - 252) = 68 , E = (68+3) =7l.

B+C+D+E = (79x4)=316.

(A+B+C+D) -(B+C+D+E)=(320 - 316)kg = 4kg.

A - E = 4 = A = (4+E)=75kg.

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13. The average age of 30 students is 9 years. If the age of their teacher is included, it becomeS 10 years. The age of the teacher (in years)is :. [Assistant Grade]

27 35

31 40


Answer: 40

Explanation: Age of the teacher = (31*10 + 30*9) = 40 years.

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14. The average of two numbers is M. If one number is N, then the other number is. [Assistant Grade]

2N M—N

2M 2M—N


Answer: 2M—N

Explanation: Sum of two numbers = 2M.

other number = (2M—N)

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15. The average salary per month of 30 employees in a compnaY is Rs 4000. If the manager’s salary is added, the average salary iicreaSeS to Rs 4300, what is the salary of the manager. [Bank P.O. 1993]

Rs 10000 Rs 12000

Rs 13000 Rs 13300


Answer: Rs 13300

Explanation: Salary of the manager = (31*4300 - 30*4000) = 13300.

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[10/15/2015 6:13:27 PM]

16. Five years ago, the average age of P and Q was 15 years. Average age of F, Q andR today is 20 years. How old will R be after 10 years?. [Bank P.O. 1989]

35 yrs 30 yrs

40 yrs 50 yrs


Answer: 30 yrs

Explanation: (P + Q), five years ago = (15 * 2) = 30 years.

(P+Q), now = (30+5*2)years=40years.

(P + Q + R), now = (20 x 3) years =60 years.

R, now = (60 - 40) years = 20 years.

R, after 10 years = (20 + 10) years =30 years.

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17. The average age of a committee of eight members is 40 years. A member aged 55 years retired and his place was taken by another member aged 39 years. The average age of the present committee is:. [Teacher’s Exam ]

39 years 36 years

38 years 35 years


Answer: 38 years

Explanation: Required average = (8*40 - 55*39)/8 = 38 years.

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18. There are three sections of a class in a school. The number of students in the three sections is 38, 32 and 40 and the average age of the students in these sections separately is 15.3 years, 16.5 years and 15.9 years respectively. What is the average age of the class?. [Hotel Managemen]

15.9 yrs15.96 yrs

15.92 yrs 15.86 yrs


Answer: 15.86 yrs

Explanation: average = (38*15.3 + 32*16.5 + 40*15.9)/(38+32+40) = 1745.4/110 = 15.867

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19. A man whose bowling average is 12.4, takes 5 wickets for 26 runs and ther eby decreases his average by 0.4. The number of wickets, taken by him before his last match is :. [C.B.I. 1991]

85 72

78 64


Answer: 85

Explanation: Let the number of wickets taken before the last match is x.

Then, (l2.4x + 26)/(x + 5) = 12 ⇒ l2.4x+26=12x+60

⇒ 0.4x=34 ⇒ x = 34/0.4 = 85

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20. A motorist travels to a place 150 km away at an average speed of 50 km per hour and returns at 30 km per hour. His average speed for the whole journey in km per hour is :. [Bank P.O. 1991]

35 37.5

37 40


Answer: 37.5

Explanation: Average speed = 2xy/(x + y) km/hr = 2*50*30/(50 + 30) = 37.5 km/hr

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[10/15/2015 6:14:08 PM]

21. The average age of boys in the class is twice the number of girls in the class. If the ratio of boys and girls in the class of 36 be 5 : 1, what is the total of the ages (in years) of the boys in the class. [Bank P.O. 1989]

490 420

196 360


Answer: 360

Explanation: Number of boys = 136 *(5/2) = 30,

Number of girls 6.

Average age of boys = (2 * 6) = 12 years.

Total age of boys (30 * 12) years = 360 years.

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22. The average of four consecutive even numbers is 27. The largest of these numbers is :. [Assistant Grade]

36 30

32 28


Answer: 30

Explanation: Let the numbers are x, x+2, x+4 and x+6. Then,

(x+x+2+x+4+x+6)/4 = 27 ⇒ 4x+ 12/4 = 27 ⇒ x + 3 = 27 ⇒ x = 24

Largest number = (x + 6) = 24 + 6 = 30.

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23. The average of ten numbers is 7. If each nuniber is multiplied by 12, then the average of new set of numbers is :. [Assistant Grade]

7 82

19 84


Answer: 84

Explanation: Average of new set = (12 x 7) = 84.

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24. In seven given numbers, the average of first four numbers is 4 and that of the last four numbers is also 4. If the average of these seven numbers is 3, the fourth number is :. [I.Tax and Centr]

3 7

4 11


Answer: 11

Explanation: Fourth number=(4*4 + 4*4 - 7*3) = 11.

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25. The average age of a class is 15.8 years. The average age of the boys in the class is 16.4 yrs while that of the girls is 15.4 years. What is the ratio of boys to girls in the class? . [Hotel Managemen]

1:2 3:5

3:4 2 : 3


Answer: 2 : 3

Explanation: Let the ratio is k : 1 . Then, k*16.4 + 1 * 15.4=(k+l)*15.8

or(16.4 - 15.8)k=(15.8-15.4) or k=0.4/0.6= 2/3.

Required ratio = 2/3 : 1 = 2 : 3

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[10/15/2015 6:16:12 PM]

26. The average of first five multiples of 3 is:. [I.Tax and Cent]

3 8

6 9


Answer: 9

Explanation: average = (1 + 2 + 3 + 4 + 5) * 3/5 = 15 * 3 / 5 = 9

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27. Three years ago, the average age of a family of 5 members was 17 years. A baby having been born, the average age of the family is the same today . The present age of the baby is: . [Assistant Grade]

2 yrs 3 yrs

2.4 yrs 1.5 yrs


Answer: 2 yrs

Explanation: Total age of 5 members, 3 years ago = (17 x 5) = 85 years.

Total age of 5 members now = (85 + 3 x 5) = 100 years.

Total age of 6 members now = (17 x 6) = 102 years.

Age of the baby =2 years.

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28. The average of first 50 natural numbers is

11.5 25.5

22.5 25


Answer: 25.5

Explanation: Sum of first n natural numbers n(n + 1)/2

So, average of first n natural numbers n(n + 1)/2n = (n + 1)/2

⇒ (50 + 1)/2 = 25.5

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29. Five years ago, the average age of A, B, C and D was 45 years. With E joining them now, the average of all the five is 49 years. How old is E? . [Bank P.O. 1988]

25 years 45 years

40 years 64 years


Answer: 45 years

Explanation: (A+B+C+D), five years ago =(45*4)= l80years.

(A+B+C+D), now = (180 + 5*4) years = 200 years.

A+B+C+D+E, now = (49x5)years=245years.

E, now = (245—200)=45years.

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30. If a, b, c, d, e are five consecutive odd numbers, their average Is: . [Bank P.O. 1989]

5(a + 4) 5(a+b+c+d+e)

abcde (a + 4)


Answer: (a + 4)

Explanation: Clearly,b=a+2,c=a+4,d=a+6 and e=a+8.

Average (a + (a + 2) + (a + 4) + (a + 6) + (a + 8)) / 5 = (5a + 20) / 5 = (a + 4)

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[10/15/2015 6:16:59 PM]

31. The average of 11 observations is 60. If the average of first five observations is 58 and that of the last five is 56, then the sixth observation is. [Assistant Grade]

90 85

110 100


Answer: 90

Explanation: Sixth observation=[60*11 - (58*5 + 56*5)] = 90.

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32. A team of 8 persons joins in a shooting competition. The best marksman scored 85 points. If he had scored 92 points; the average score for the team would have been 84. The number of points, the team scored, was :. [C.B.I. 1993]

672 645

665 588


Answer: 665

Explanation: Let the total score be x.

(x +92 - 85)/8 = 84 so x+7 = 672 so x=665

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33. The average of eight numbers is 14. The average of six of these numbers is 16. The average of the remaining two numbers is: . [Bank P.O. 1994]

4 16

8 Data inadequate


Answer: 8

Explanation: Total sum of remaining two (8*14 - 6*16) = 16.

Average oLthese two numbers = 16/2 = 8

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34. Of the three numbers, second is twice the first and is also thrice the third. If the average of the three numbers is 44, the largest number is:. [I Tax and Centr]

24 72

36 108


Answer: 24

Explanation: Let 3rd number is x. Then, second number = 3x.

First number = 3x / 2

(x + 3x + 3x)/2 = (44*3) or 11x/2 = 44*3 or x=24.

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35. The mean of 1², 2², 3², 4², 5², 6², 7² is:. [U.D.C. Exam 199]

40 30

20 10


Answer: 20

Explanation: sum of square of first n numbers n(n + 1)(2n + 1)/6

⇒ 7(7 + 1)(7*2 + 1)/6 = 140

average = 140/7 = 20

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[10/15/2015 6:17:24 PM]

36. The average weight of 9 mangoes increases by 20 g if one of them weighing 120 g is replaced by another. The weight of the new mango is :. [AssistaDt Grade]

180 g 260 g

200 g 300 g


Answer: 300 g

Explanation: Total weight increased (9*20) gm = 180 gm.

Weight of new mango = (120 + 180) gm = 300gm.

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