Number System-Railway Maths Part V

Total Questions: 50

1. Rationalising factor of ³√40 is: [RRB NTPC 20/01/2021 (Evening)]

Correct Answer: (b) 5⅔
Solution:

³√40, = ³√2 × 2 × 5, 3) = 2 × ³√5, = 2 × 5⅓ The rationalizing factor of an irrational number is a number that must be multiplied by that irrational number to make it rational. There might be many rationalizing factors of an irrational number but we must find the simplest number that must make it rational when multiplied by it.
To make (2 × 5⅓) rational, we have to multiply it by (5⅔)

2. The greatest prime number less than 200 is: [RRB NTPC 21/01/2021 (Evening)]

Correct Answer: (a) 199
Solution:

The greatest prime number less than 200 = 199
Because prime numbers are a number that can be divided exactly only by itself and 1, for example 7, 17, 41 and 199 etc.

3. What will be the value if you multiply 2/11 by the multiply by the reciprocal of - 5/14 ? [RRB NTPC 21/01/2021 (Evening)]

Correct Answer: (c) - 28/55
Solution:

According to the question,
= 2 11 × (reciprocal of - 5/14 )
= 2/11 × (- 14/5) = - 28/55

4. An irrational number between 3 and 5 is: [RRB NTPC 22/01/2021 (Morning)]

Correct Answer: (a) √17
Solution:

3 = √9 and 5 = √25
If we find irrational numbers between 3 and 5, it means that the number lies between √9 and √25 .
√17 lies between √9 and √25

5. Which of the following has terminal decimal representation? [RRB NTPC 22/01/2021 (Morning)]

Correct Answer: (b) 2/5
Solution:

Hence, we can see that only 2/5 has terminal decimal.

6. Which of the following statements is false? [RRB NTPC 22/01/2021 (Morning)]

Correct Answer: (c) All natural numbers together with zero are called integers.
Solution:

integers are numbers that can be positive, negative or zero, but cannot be a fraction.

7. How many prime numbers are there that are less than 50? [RRB NTPC 22/01/2021 (Evening)]

Correct Answer: (c) 15
Solution:

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47 are the prime numbers that are less than 50.

8. Find the place value of 7 in 71,624. [RRB NTPC 23/01/2021 (Morning)]

Correct Answer: (a) 70,000
Solution:

Given number = 71 ,624
Place value of 7 = 70000

9. The sum of the four consecutive even numbers is 484. What would the smallest number be? [RRB NTPC 23/01/2021 (Morning)]

Correct Answer: (a) 118
Solution:

Let the numbers be x, x + 2, x + 4, x + 6
A/Q, x + x + 2 + x + 4 + x + 6 = 484
⇒ 4x + 12 = 484 ⇒ 4x = 472
⇒ x = 472/4 = 118 (Smallest no.)

10. Find the difference of face values of 9 and 3 in 3, 15, 298. [RRB NTPC 23/01/2021 (Morning)]

Correct Answer: (a) 6
Solution:

The given number = 3,15,298
Face value of 9 = 9
Face value of 3 = 3
Difference =9 - 3 = 6