Exercise on Averages – 1

1. The average of a list of 6 numbers is 20. If we remove one of the numbers, the average of the remaining numbers is 15. What is the number that was removed?

2. A class of 25 students took a GK test. 10 students had an average score of 80. The other students had an average score of 60. What is the average score of the whole class?

3. The mean of 6 observations was found to be 40. Later it was detected that among the given observations 82 was misread as 28. The correct mean is __

4. How much Sachin Tendulkar’s average increase by after he scores a 100 in his 100th innings assuming that he current strike rate is 50.

5. The workers of the company ‘Corrupt Judges INC’, the average monthly salary of 50 workers was a meagre amount of Rs. 680. It was later discovered that one worker received Rs. 270 instead of Rs. 720. What was the correct average monthly salary?

6. The average age of a husband, his wife and son 3 years ago was 27 years and that of his wife and son 5 years ago was 20 years. What is the husband’s present age?

7. The average temperature of all 7 days of the week is 30, that of the first 3 days is 28 and of the next 3 days is 31. What is the temperature on the last day of the week?

8. The average age of A and B is 20 years. If C replace A the average would be 19 and if C replaces B the average would be 21. What are the ages of A, B and C?

9. In the first 10 overs of a cricket game, the run rate was only 3.2. What should be the run rate in the remaining 40 overs to reach the target of 282 runs?

10. The average weight of 8 person's increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg. What might be the weight of the new person?

11. A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is:

12.  A family consists of grandparents, 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?

13. The average age of a group of 10 students was 20. The average age increased by 2 years when two new students joined the group. What is the average age of the two new students who joined the group?

14.   In a class of boys and girls, the average age of 40 boys is 13.5 years and that of girls is 13 years. The average age of whole class is 13.4 years. Find the number of girls in the class.

15. Average of every possible pair out of the three given numbers is 33, 39 and 48. What is the average of the three numbers?

16.  The average of A, B, C and D is 16. Half the sum of B, C and D is 28. What is the value of A?

17. A boy purchased 12 copies of a book at Rs.33 per copy and 24 copies of another book at Rs.38 per copy. Find the average price of the books.

18. The average of eight scores is 87. Of these, the highest score is 2 more than the second highest score in magnitude. If these two scores are eliminated, then the average of the remaining scores is 85. What was the highest score?

19. In a class there are B boys with an average age of 16 years. One boy of 17 years leaves the class and another boy of 12 years joins. If the average age now is 15 years, then what is the value of B?  

20.   The average height of 30 boys, out of a class of 50 boys, is 160 cm. If the average height of the remaining boys is 165 cm, then what is the average height of the whole class?

21.  The average of 7 numbers is 35 and if the 7th number is 11, the average of the remaining 6 numbers is

22. Average of eight numbers is 10. If each number is multiplied by 12, then find the average of the new set of numbers.

23.  Average of a set of three numbers is 30. Each number is first increased by 6 and then divided by 2. Find the new average?

24. Average age of a group of 32 boys is 25 years. Eight new boys with average age of 20 years are added to the group. Find the average age of the new group.

25. The cost/kg of coffee for 3 successive years was Rs. 10, Rs. 12 and Rs. 15. If Rs. 7,200 were spent every year, then what is the average cost/kg of coffee for 3 years?


  1. Sir, Can u please explain me the 19th and the 25th solution
    In 19 i m getting option 2 i.e 5 as answer…. 
    In 25th question, i have solved it this way,
    As Rs. 7200 is spent evry year, therefore total commodity purchased for three years – 720+600+480= 1800kg 
    Then Average cost = 7200/1800=4 
    how can we get 12 as answer

    • 7200 is spent annually so if u are taking 7200 (average of 3 years, do the same with the quantity) then take 600 now solve it u may get the answer to your doubt.

  2. Sir, 
    With due respect ,I am not satisfied answer of  question no.19 ,answer is given in your result sheet is 2.8 but in my solution it is 5,May kindly explain your solution ,i shall be very thankful to you.
    with regards

Post a comment or at least a 'thank you!' It's okay if you're ungrateful. :P