Average (Railway Maths) (Part – I)

Total Questions: 50

11. The average salary of the entire staff of an office is Rs.3,560 per month. The average salary of the officers is Rs.5,400 per month and that of non-officers is Rs.2,600 per month. If the number of officers is 12, find the number of non-officers in the office. [NTPC CBT - I 30/12/2020 (Evening)]

Correct Answer: (d) 23
Solution:

12. The difference between the mean of first 5 composite numbers and the mean of the first five prime numbers is ? [NTPC CBT - I 07/01/2021 (Morning)]

Correct Answer: (a) 1.8
Solution:

13. If the average of a₁, a₂, a₃ and a₄ is 19.5, a₁ = 21 and the average of a₁, a₂ and a₃ is equal to the average of a₂, a₃ and a₄, then what will be the value of a₄? [NTPC CBT - I 17/01/2021 (Morning)]

Correct Answer: (d) 21
Solution:

14. Sonal was given some money to take care of her travel expenses during a 16-days sales drive. However, she had to increase her stay by another 8 days, as a result her average daily travel allowance went down by Rs. 80. How much was allowance to her in the beginning? [NTPC CBT - I 17/02/2021 (Evening)]

Correct Answer: (b) Rs. 3,840
Solution:

15. The average marks obtained by a group of 25 students was 36. One student left the group, as a result of which the average of the remaining students rose to 37.5. Soon after another student joined the same group, as a result of which the average marks dropped to 37.2. Find the average marks of the student who left and the student who joined the group. [NTPC CBT - I 03/03/2021 (Evening)]

Correct Answer: (b) 15
Solution:

16. The mean of a distribution is 14 and standard deviation is 5. Find the coefficient of variation. [RRB JE 01/06/2019 (Morning)]

Correct Answer: (d) 35.7%
Solution:

17. In a class, there were 9 boys and some girls. In a test the average score obtained by the boys was 12 while that obtained by the girls was 14. If the overall average was 13.1, what was the total number of students in the class? [RRB ALP Tier - I 09/08/2018 (Morning)]

Correct Answer: (d) 20
Solution:

18. After 10 innings the average score per innings of a batsman was 52. After 12 innings the average rose to 54. If the batsman had scored 16 more runs in the 12ᵗʰ innings than in the previous one, how many runs did he score in the 11th innings? [RRB ALP Tier - I 14/08/2018 (Morning)]

Correct Answer: (c) 56
Solution:

19. The average marks obtained by a group of 10 students were 20. One student left the group as a result of which the average of the remaining students rose to 21. But another student joined, as a result of which the average marks of the group dropped a bit and became 20.6. What were the average marks obtained by the student who left and the one who joined? [RRB ALP Tier - I 17/08/2018 (Evening)]

Correct Answer: (a) 14
Solution:

20. The expenditure of a company was Rs.32,400 during the first quarter of the Financial Year, Rs.21,600 during the second quarter of the Financial Year, Rs.79,200 for the third quarter of the Financial Year. If overall quarterly average expenditure during the whole Financial Year is Rs.50,400, find the expenditure for the last quarter of the Financial Year (in Rs.). [RPF Constable 18/01/2019 (Morning)]

Correct Answer: (d) 68,400
Solution: