Number System-Railway Maths Part IV

Total Questions: 50

31. A number when divided by 280 leaves 73 as the remainder. When the same number is divided by 35. The remainder will b: [RRB NTPC 16/01/2021 (Morning)]

Correct Answer: (a) 3
Solution:

The number which is divisible by 280 will also be divisible by 35.
So we have to check only the remainder.
73/35 ⇒ Remainder = 3

32. If a positive number when decreased by 3, is equal to 28 times the reciprocal of the number, then find the number. [RRB NTPC 16/01/2021 (Morning)]

Correct Answer: (d) 7
Solution:

Let the Number = x
A/Q, x - 3 = 28/x
⇒ x(x - 3) = 28 = 7 × 4
On comparing we get x = 7

33. The difference of two numbers is 20% of the larger number. If the smaller number is 40, then find the larger number. [RRB NTPC 16/01/2021 (Morning)]

Correct Answer: (d) 50
Solution:

Let the bigger number = x
As per the question, x - 40 = x/5
⇒ x - x/5 = 40 ⇒ 4x/5 = 40 ⇒ x = 50

34. Find the greatest ratio in the following. [RRB NTPC 16/01/2021 (Morning)]

Correct Answer: (d) 19 : 27
Solution:

On comparing all, the greatest rational number 19/27
So this will be the greatest ratio.

35. Find the smallest number which must be subtracted from 63535 to make it a perfect square. [RRB NTPC 17/01/2021 (Morning)]

Correct Answer: (b) 31
Solution:


31 must be subtracted from 63535 to make it a perfect square.

36. How many digits will be there to the right of the decimal point on the product of 99.75 and 0.05554? [RRB NTPC 17/01/2021 (Morning)]

Correct Answer: (b) 6
Solution:

99.75 × 0.05554 = 5.540115 6 digits will be here to the right of the decimal.

37. The smallest positive number which must be added to the greatest number of 4 digits in order that the sum may be exactly divisible by 307 is: [RRB NTPC 17/01/2021 (Evening)]

Correct Answer: (c) 132
Solution:

Greatest number of four digit = 9999
When we divide 9999 by 307 we get 175 as Remainder.
Required number = 307 - 175 = 132

38. Find the smallest perfect square number which must be added to the number 12519 to get a perfect square number. [RRB NTPC 17/01/2021 (Evening)]

Correct Answer: (d) 25
Solution:

39. The number whose only factors are 1 and the number itself is called a/an_____ number. [RRB NTPC 18/01/2021 (Morning)]

Correct Answer: (b) prime
Solution:

The number whose only factors are 1 and the number itself is called a Prime number.
e.g. 2,3,5,7,......

40. If 111.....1 (n digits) is divisible by 9, then the least value of n is__ [RRB NTPC 18/01/2021 (Morning)]

Correct Answer: (a) 9
Solution:

If 111.....1 (n digits) is divisible by 9,
Then the value of n will be = 9
Because as we know to be divisible by 9,
the sum of the digits has to be = 9 or a multiple of 9.
Here (1 + 1 + 1 +1+1+1+1+ 1 + 1) = 9
So, the least value of n = 9