Mathematical Operations – Railway Reasoning (part – 4)

Total Questions: 50

1. Assuming P & Q were Arithmetic Operators, if 24 P 12 Q 13 = 15 and 16 Q 56 P 14 = 20, then 87 P 29 Q 22 = ? [RRB NTPC 21/01/2021 (Evening)]

Correct Answer: (c) 25
Solution:

Let , P = ÷ , Q = +
Then , 24 P 12 Q 13
= 24 ÷ 12 + 13 = 15 (satisfied)
Now for 87 P 29 Q 22 = 87 ÷ 29 + 22
= 3 + 22 = 25

2. If ‘×’ means ‘−’, ‘#’ means ‘+’, ‘@’ means ‘=’, ‘$’ means ‘÷’ and ‘&’ means ‘×’, then which of the following equations is true? [RRB NTPC 25/01/2021 (Morning)]

Correct Answer: (b) (15 × 4) & 3 @ (60 $ 2) # 3
Solution:

On checking options one by one, we find that option (b) satisfies.
⇒ (15 × 4) & 3 @ (60 $ 2) # 3
⇒ (15 − 4) × 3 = (60 ÷ 2) + 3
⇒ 11 × 3 = 30 + 3 ⇒ 33 = 33
⇒ LHS = RHS

3. Which of the two signs in the given options, if interchanged, would NOT impact the correctness of the following equation ? [RRB NTPC 25/01/2021 (Morning)]

3 × 5 + 3 − 18 ÷ 3 = 12

Correct Answer: (b) × and +
Solution:

On interchanging ‘×’ and ‘+’, the equation still remains correct.
⇒ 3 × 5 + 3 − 18 ÷ 3 = 12
⇒ 3 + 15 − 6 = 12 ⇒ 12 = 12

4. Which two signs have to be interchanged to make the following equation correct? [RRB NTPC 25/01/2021 (Evening)]

15 - 3 + 40 ÷ 5 × 30 = 23

Correct Answer: (b) - and ×
Solution:

⇒ 15 × 3 + 40 ÷ 5 - 30 = 23
⇒ 23 = 23 (LHS = RHS)

5. If ‘÷’ stands for ×, ‘+’ stands for /, ‘×’ stands for +, and ‘/’ stands for -, then find the value of 24 + 6/2 − 9 × 4. [RRB NTPC 27/01/2021 (Morning)]

Correct Answer: (c) -10
Solution:

24 + 6/2 − 9 × 4.
After interchanging
= 24 / 6 - 2 × 9 + 4 = 4 - 18 + 4 = -10

6. If ‘×’ stands for ‘+’, ‘+’ stands for ÷, ‘-’ stands for ‘×’ and ÷ stands for ‘-’, then find the value of: [RRB NTPC 29/01/2021 (Morning)]

100 ÷ 5 − 6 + 1 × 6

Correct Answer: (a) 76
Solution:

Given:
100 ÷ 5 − 6 + 1 × 6
After changing signs, we get:
100 - 5 × 6 ÷ 1 + 6 = 100 - 5 × 6 + 6
= 100 - 30 + 6 = 76

7. If ‘A’ stands for ‘-’, ‘B’ stands for ‘+’, and ‘C’ stands for ‘×’, then what will be the value of 9C5B10A5C12? [RRB NTPC 29/01/2021 (Evening)]

Correct Answer: (c) -5
Solution:

9 C 5 B 10 A 5 C 12
= 9 × 5 + 10 − 5 × 12
= 45 + 10 - 60 = -5

8. If ‘÷’ stands for ‘addition’, ‘+’ stands for ‘subtraction’, ‘×’ stands for ‘division’ and ‘-’ stands for ‘multiplication’, then which of the following equations will be correct. [RRB NTPC 30/01/2021 (Evening)]

Correct Answer: (a) 5 ÷ 12 × 4 - 3 + 8 = 6
Solution:

By hit and trial method and changing sign as per question we get,
5 + 12 ÷ 4 × 3 - 8 = 6
From LHS, 5 + 9 - 8 ⇒ 6 (RHS)

9. If ‘+’ means division, ‘-’ means addition, ‘×’ means subtraction, ‘÷’ means multiplication. Then what will be the value of the following expression: [RRB NTPC 02/02/2021 (Morning)]

Correct Answer: (a) 2
Solution:

10. If J denotes addition , G denotes subtraction, M denotes multiplication, and B denotes division, then which of the following equations will NOT be correct? [RRB NTPC 04/02/2021 (Morning)]

Correct Answer: (d) 6 B 2 M 8 G 10 J 4 = 20
Solution:

This type of question uses hit and trial method. = 6 B 2 M 8 G 10 J 4
= 6 ÷ 2 × 8 - 10 + 4 = 3 × 8 - 10 + 4
= 24 - 10 + 4 = 28 - 10 = 18 ≠ 20