Number System-Railway Maths Part VI

Total Questions: 50

11. If the numbers from 1 to 26 that are divisible by 2 are arranged in descending order, which number will be at the 9th place from the bottom ? [RRB NTPC 04/02/2021 (Evening)]

Correct Answer: (a) 18
Solution:

Descending order of numbers divisible by 2 from 1 to 26
26, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6, 4 2,
Number which will be at the 9th from the bottom = 18

12. What is the sum of the squares of the numbers from 1 to 12? [RRB NTPC 04/02/2021 (Evening)]

Correct Answer: (d) 650
Solution:

Sum of squares of natural Number n(n + 1)(2n + 1)/6
= (12 × 13 × 25)/6 = 650

13. Find the square root of 42.25. [RRB NTPC 05/02/2021 (Morning)]

Correct Answer: (a) 6.5
Solution:

√4225 = 65
So that, √42.25 = 6.5

14. The decimal representation of 5/100 + 2/5 - 6/25 is: [RRB NTPC 05/02/2021 (Morning)]

Correct Answer: (b) 0.21
Solution:

5/100 + 2/5 - 6/25
= 5 + 40 - 24/100 = 0.21

15. How many of the integers between 109 and 121, both inclusive, are prime numbers? [RRB NTPC 08/02/2021 (Morning)]

Correct Answer: (c) 2
Solution:

109 and 113 are two integers and they are prime between 109 and 121.
(Including 109 and 121)

16. The sum of the greatest and smallest numbers of six digits is: [RRB NTPC 08/02/2021 (Morning)]

Correct Answer: (c) 1099999
Solution:

six digits greatest number = 999999
and six digit smallest number = 100000
The sum of the greatest and smallest numbers of six digits = 1099999

17. On dividing 15,971 by a certain number, the quotient is 55 and the remainder is 21. Find the divisor. [RRB NTPC 08/02/2021 (Morning)]

Correct Answer: (c) 290
Solution:

15971 = x × 55 + 21
15950 = x × 55 → x = 290

18. What is the smallest four digit number formed by using the digits 3, 5, 0,6? [RRB NTPC 08/02/2021 (Morning)]

Correct Answer: (d) 3056
Solution:

Smallest four digit number formed by using the digits 3, 5, 0, 6 = 3056

19. What is the sum of the cube of the natural numbers from 1 to 10, both inclusive? [RRB NTPC 08/02/2021 (Morning)]

Correct Answer: (b) 3025
Solution:

1³+ 2³ + 3³ + 4³ + 5³ + 6³ + 7³ + 8³ + 9³+ 10³ = 3025 or
Sum of cubes of natural numbers

20. If 58 out of 100 students in a school are boys, then express the part of the school that consists of boys in decimal. [RRB NTPC 08/02/2021 (Evening)]

Correct Answer: (a) 0.58
Solution:

Boys/Total student = 58/100 = 0.58