Mathematical Operations – Railway Reasoning (part – 3)

Total Questions: 50

41. If C means cube, A means '+', B means '-', D means '×' and E means ÷, then solve the following. [RRB NTPC 05/01/2021 (Evening)]

{((3A6) × (6B3)) E ((6B4) A (3B2))} C = ?

Correct Answer: (a) 729
Solution:

{((3 A 6) × (6 B 3)) E ((6 B 4) A (3 B 2))} C =
{((3 + 6) × (6 − 3)) ÷ ((6 − 4)
+ (3 − 2))}³
= {(9 × 3) ÷ (2 + 1)}³
= {(27 ÷ 3)}³ = 9³ = 729

42. If p + q implies p - q, p - q implies p × q, p × q implies p ÷ q and p ÷ q implies p + q, then find value of 5 + 6 - 75 × 15 ÷ 30. [RRB NTPC 08/01/2021 (Morning)]

Correct Answer: (c) 5
Solution:

Given expression:
5 + 6 − 75 × 15 ÷ 30
After changing signs as per the given instructions, we get:
= 5 - 6 × 75 ÷ 15 + 30
= 5 - 6 × 5 + 30 = 5 - 30 + 30
= 35 - 30 = 5

43. If P means '+', Q means '-', R means '×' and 'S means '÷', then find the value of the following expression. [RRB NTPC 09/01/2021 (Morning)]

2/3   S   1/3   Q   7   P   7   R   5

Correct Answer: (c) 30
Solution:

After putting the correct signs,

44. If '÷' means '+', '+' means '-', '-' means '×' and '×' means '÷'. Then what will be the value of [RRB NTPC 10/01/2021 (Evening)]

16 ÷ 4 × 2 + 5 – 3 be

Correct Answer: (a) 3
Solution:

According to question ,
16 + 4 ÷ 2 - 5 × 3
= 16 + 2 - 15 = 18 - 15 = 3.

45. If + means “×”, ‘×’ means ‘-’, ‘÷’ means ‘+’, then which of the following would be the value of 14 ÷ 2 + 8 × 5? [RRB NTPC 11/01/2021 (Morning)]

Correct Answer: (c) 25
Solution:

14 ÷ 2 + 8 × 5
= 14 + 2 × 8 - 5 = 14 + 16 - 5 = 25

46. If ‘÷’ means ‘+’, ‘-’ means ‘×’, ‘×’ means ‘-’, and ‘+’ means ‘÷’. Find the value of: 40 ÷ 20 × 10 + 10 – 5. [RRB NTPC 12/01/2021 (Morning)]

Correct Answer: (a) 55
Solution:

40 ÷ 20 × 10 + 10 - 5
= 40 + 20 - 10 ÷ 10 × 5 = 40 + 20 - 1 × 5
= 40 + 20 - 5 = 60 - 5 = 55

47. Which two signs (mathematical operators) should be interchanged to make the given equation correct? [RRB NTPC 16/01/2021 (Morning)]

56 - 8 + 42 ÷ 6 × 5 = 19

Correct Answer: (d) ÷ and -
Solution:

56 - 8 + 42 ÷ 6 × 5 = 19
Interchange ÷ and -
⇒ 56 ÷ 8 + 42 - 6 × 5
= 7 + 42 - 30 = 49 - 30 = 19 = RHS

48. If “+” means division, “÷” means multiplication, “-” means addition and “×” means subtraction, then find the value of 15 + 3 – 8 ÷ 9 × 7. [RRB NTPC 18/01/2021 (Morning)]

Correct Answer: (d) 70
Solution:

Given :
15 + 3 - 8 ÷ 9 × 7
After changing signs in the above expression, we get:
15 ÷ 3 + 8 × 9 - 7 = 5 + 72 - 7 = 70

49. If ‘+’ means ‘÷’, ‘-’ means ‘×’, ‘÷’ means ‘+’ and ‘×’ means ‘-’, then find the value of the following expression. [RRB NTPC 18/01/2021 (Evening)]

11 - 2 × 4 ÷ 12 + 4

Correct Answer: (c) 21
Solution:

‘+’ means ‘÷’, ‘-’ means ‘×’, ‘÷’ means ‘+’ and ‘×’ means ‘-’.
Then the value of the following
expression : 11 - 2 × 4 ÷ 12 + 4
= 11 × 2 - 4 + 12 ÷ 4 = 18 + 3 = 21

50. If ‘+’ means ‘subtract’, ‘-’ means ‘addition’, ‘÷’ means ‘multiplication’ and ‘×’ means ‘divisible’, then what is the value of (8 + 2 - 19) - (4 + 27 × 3)? [RRB NTPC 21/01/2021 (Morning)]

Correct Answer: (b) 150
Solution:

Given: (8 + 2 - 19) - (4 + 27 × 3)
After changing signs as per the instructions, we get:
(8 - 2 × 19) × (4 - 27 ÷ 3)
(8 - 38) × (4 - 9) = (-30) × (-5) = 150