Mathematical Operations – Railway Reasoning (part – 1)

Total Questions: 50

11. If ‘÷’ stands for ‘addition’, ‘+’ stands for ‘subtraction’, ‘×’ stands for ‘division’, and ‘-’ stands for ‘multiplication’, then which of the following equations will NOT be correct? [NTPC CBT - I 30/01/2021 (Evening)]

Correct Answer: (a) 36 - 4 × 3 + 6 ÷ 16 = 60
Solution:

By hit and trial method and changing sign as per question we get,
36 – 4 × 3 + 6 ÷ 16 = 60
36 × 4 ÷ 3 – 6 + 16 = 60
48 – 6 + 16 ≠ 60 ( its not correct )

12. Select the combination of mathematical symbols from among the given options that when sequentially placed in the blank boxes will result in a balanced equation. [NTPC CBT - I 02/02/2021 (Evening)]

57 □ 3 □ 2 □ 2 □ 15 □ 25

Correct Answer: (b) ÷, ×, +, =, +
Solution:

57 ÷ 3 × 2 + 2 = 15 + 25
40 = 40 (LHS = RHS)

13. In the series below, different letters stand for various mathematical operations and symbol indicated as : [NTPC CBT - I 16/02/2021 (Morning)]

P ; +, Q ; -, R ; ×, S ; ÷, T ; =, U ; > V ; <
Choose the options which is correct according to the given operations and symbols

Correct Answer: (d) 15 S 3 R 4 T 4 R 5
Solution:

15 S 3 R 4 T 4 R 5
⇒ 15 ÷ 3 × 4 = 4 × 5
⇒ 5 × 4 = 4 × 5 ⇒ 20 = 20

14. After interchanging ‘÷’ and ‘×’, and interchanging ‘2’ and ‘1’, which of the following equations is correct? [NTPC CBT - I 09/03/2021 (Morning)]

Correct Answer: (c) 3 ÷ 1 + 3 × 3 – 2 = 6
Solution:

3 ÷ 1 + 3 × 3 – 2
After interchanging
= 3 × 2 + 3 ÷ 3 – 1 = 3 × 2 + 1 – 1
= 6 + 1 – 1 = 6 = RHS

15. If K = 8, L = 5, N = 4 and T = 28, then what will be the value of T ÷ N × L + K? [NTPC CBT - I 27/03/2021 (Morning)]

Correct Answer: (a) 43
Solution:

Given,
K = 8, L = 5, N = 4 and T = 28
= T ÷ N × L + K = 28 ÷ 4 × 5 + 8
= 7 × 5 + 8 = 35 + 8 = 43

16. Which of the following equations is INCORRECT? [NTPC CBT - I 07/04/2021 (Evening)]

Correct Answer: (c) 13 - 7 + 8 × 9 + 63 ÷ 7 = 86
Solution:

13 - 7 + 8 × 9 + 63 ÷ 7 = 86
= 13 - 7 + 72 + 9 = 94 - 7 = 87 ≠ 86

17. In a certain code language, '+' to '×' is expressed, '÷' to '+' is expressed, '-' to '÷' and '×' to '-' expressed. Find the answer to the following question. [ALP Tier II 23/01/2019 (Morning)]

12 ÷ 6 - 2 + 10 × 5 = ?

Correct Answer: (a) 37
Solution:

Given expression :
12 ÷ 6 - 2 + 10 × 5
After interchanging the sign,
12 + 6 ÷ 2 × 10 - 5 = 12 + 3 × 10 - 5
= 12 + 30 - 5 = 37

18. Which of the following signs and numbers should be interchanged such that for the following expression, LHS = RHS. [RRB ALP Tier - I 29/08/2018 (Morning)]

6 × 4 + 2 = 16

Correct Answer: (b) × with +, 4 with 6
Solution:

6 × 4 + 2 = 16
On checking the options one by one, we get on changing × with +, 4 with 6, the equation satisfies :
4 + 6 × 2 = 16
16 = 16
LHS = RHS

19. If ‘+’ means ‘÷’, ‘-’ means ‘×’, ‘×’ means ‘+’, ‘÷’ means ‘-’, what will come in place of the question mark (?) in the following equation? [Group - D 17/08/2022 (Afternoon)]

16 + 4 - 8 ÷ 3 × 2 = ?

Correct Answer: (c) 31
Solution:

16 + 4 - 8 ÷ 3 × 2
After interchanging signs according to given conditions in the question, we get
⇒ 16 ÷ 4 × 8 - 3 + 2 = 32 - 3 + 2
= 31

20. What will come in place of the question mark (?) in the following equation, if '-' is interchanged with ‘×’ and ‘÷’ is interchanged with ‘+’? [Group - D 17/08/2022 (Evening)]

6 ÷ 16 × 4 ÷ 9 - 8 + 2 × 7 = ?

Correct Answer: (a) 47
Solution:

After interchanging the signs required equation is
6 + 16 - 4 + 9 × 8 ÷ 2 - 7
= 22 - 4 + 36 - 7 = 47