Average Problems Aptitude Questions and Answers

Best Practice Questions on Averages Aptitude Questions and Answers

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Formulas of Average Questions Answers MCQs

1. Average = [Sum of observations / Number of observations]

2. Suppose a man covers a certain distance at x kmph and an equal distance at y kmph. Then, the average speed during the whole journey is [2xy / x + y] kmph.

 

Average - Aptitude Solved Questions and Answers

1. Find the average of all prime numbers between 30 and 50.

Sol: There are five prime numbers between 30 and 50.

They are 31, 37, 41, 43 and 47.

=> Required average = [(31 + 37 + 41 + 43 + 47) / 5]

                    = 199/5

                    = 39.8.

 

2. Find the average of first 40 natural numbers.

Sol: Sum of first n natural numbers = 40 x 41 / 2

                                    = 820.

=> Required average = 820 / 40

                    = 20.5.

 

3. A batsman makes a score of 87 runs in the 17th inning and thus increases his average by 3. find his average after 17th inning.

Sol: Let the average after 17th inning = x.

Then, average after 16th inning        = (x - 3)

=> 16(x - 3) + 87 = 17x or x = (87 - 48) = 39.

 

4. 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.

Sol: Number of boys = 136 x (5/2)

                    = 30,

Number of girls 6.

Average age of boys = (2 x 6)

                    = 12 years.

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

 

5. The average of four consecutive even numbers is 27. The largest of these numbers is

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.

 

Quantitative Aptitude - Average Questions

1. 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?

A. 8 years 

B. 12 years

C. 10 years 

D. 14 years

Ans: B

Explanation :

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

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

 

2. The average of eight numbers is 14. The average of six of these numbers is 16. The average of the remaining two numbers is:

A. 4 

B. 16

C. 8 

D. Data inadequate

Ans: C

Explanation :

Total sum of remaining two (8 x 14 - 6 x 16) = 16.

Average of these two numbers = 16/2 = 8

 

3. 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 :

A. 35 

B. 37.5

C. 37 

D. 40

Ans: B

Explanation :

Average speed = 2xy/(x + y) km/hr

                   = 2 x 50 x 30/(50 + 30)

                   = 37.5 km/hr

 

4. 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.

A. 90 

B. 85

C. 110 

D. 100

Ans: A

Explanation :

Sixth observation = [60 x 11 - (58 x 5 + 56 x 5)]

 

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

A. 3 

B. 8

C. 6 

D. 9

Ans: D

Explanation :

average = (1 + 2 + 3 + 4 + 5) x 3/5

             = 15 x 3 / 5

             = 9

 

6. If a, b, c, d, e are five consecutive odd numbers, their average Is:

A. 5(a + 4) 

B. 5(a+b+c+d+e)

C. abcde 

D. (a + 4)

Ans: D

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)

 

7. The average score of a cricketer for ten matches is 38.9 runs. If the average for the first six matches is 42, then find the average for the last four matches.

A. 33.25

B. 33.5

C. 34.25

D. 35

Ans: C

Explanation :

Total sum of last 4 matches = (10 x 38.9) – (6 x 42)

                                         = 389 - 252

                                         = 137

    Average = 137/4

                  = 34.25

 

8. David obtained 76, 65, 82, 67 and 85 marks (out of 100) in English, mathematics, physics, chemistry and biology. What are his average marks?

A. 65

B. 69

C. 75

D. None of above

Ans: C

Explanation :

Average  = (76+65+82+67+85 / 5 )

               =  375 / 5

               =  75

Hence average =  75

 

9. The average age of a husband and his wife was 23 years at the time of their marriage. After five years they have a one year old child. What is the average age of the family ?

A. 21 years

B. 20 years

C. 18 years

D. 19 years

Ans: D

Explanation :

Total of the age of husband and wife = 2×23=46

Total of the age of husband and wife after 5 years + Age of the 1 year old child

                                              = 46+5+5+1=57

Average age of the family = 57 / 3

                                              = 19

 

10. In a class, the average age of 30 boys is 13 years and the average of 20 girls is 12 years. what is the average age of the whole class?

A. 12.5 Yrs

B. 14.2 Yrs

C. 12.3 Yrs

D. 12.6 Yrs

E. None of these

Ans: D

Explanation :

Total age of 50 students

= (30X 13+20 X 12) = 630

Average  = 630/50

                 = 12.6 Years

 

11. A man spends Rs. 1600 per month on an average for the first three months, Rs 1550 for next four months and Rs. 1800 per month for the last five months and saves Rs 5200 a year What is his average monthly income?

A. Rs. 2050

B. Rs. 2100

C. Rs. 1950

D. Rs. 2200

E. None of these

Ans: B

Explanation :

 

12. The average age of father and his two sons is 27 Y ears. Five years ago, the average age of the two sons was 12 Y ears. If the difference between the ages of the two sons is four years, what is the present age of the father?

A. 42

B. 48

C. 44

D. 47

E. None of these

Ans: D

Explanation :

 

13. The average of five numbers is 27. If one number is excluded, the average becomes 25. The excluded number is:

A. 25

B. 27

C. 30

D. 35

Ans: D

Explanation :

                  

14. 3 year ago, the average 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

A. 1 year

B. 1.5 year

C. 2 year

D. 3 year

Ans: C

Explanation :

 

15. If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55 and 60, then the average marks of all the students is:

A. 53.33

B. 54.68

C. 55

D. None of these

Ans: B

Explanation :