Mathematical Operations – Railway Reasoning (part – 4)

Total Questions: 50

11. If ‘÷’ stands for ‘subtraction’, ‘×’ stands for ‘division’, ‘+’ stands for ‘multiplication’ and ‘-’ stands for ‘addition’ then which of the following equations is correct? [RRB NTPC 04/02/2021 (Evening)]

Correct Answer: (d) 12 × 4 - 7 ÷ 2 + 3 = 4
Solution:

12 × 4 - 7 ÷ 2 + 3 = 4
⇒ 12 ÷ 4 + 7 - 2 × 3
⇒ 3 + 7 - 6 = 4 = RHS

12. Which equations would become correct if we interchange the signs ‘×’ and ‘÷’ as well as the digits ‘2’ and ‘4’? [RRB NTPC 08/02/2021 (Evening)]

Correct Answer: (c) 12 × 4 ÷ 42 = 168
Solution:

12 × 4 ÷ 42
= 14 ÷ 2 × 24 = 7 × 24 = 168 = RHS

13. If + means ‘division’, - means ‘addition’, ‘×’ means ‘subtraction’ and ‘÷’ means ‘multiplication’, then what will be the value of the following expression? [RRB NTPC 08/02/2021 (Evening)]

(5/2 × 2) + (3 - 1)

Correct Answer: (b) 2
Solution:

( 5/2 × 2 ) + (3 - 1)
= (5 × 2 - 2) ÷ (3 + 1)
= (10 - 2) ÷ 4 = 8 ÷ 4 = 2

14. Select the combination of mathematical signs that when sequentially placed in the blanks of the given equation will balance the equation. [RRB NTPC 08/02/2021 (Evening)]

12 _ 3 _ 12 _ 24

Correct Answer: (a) × - =
Solution:

12 _ 3 _ 12 _ 24
= 12 × 3 - 12 = 24
⇒ 36 - 12 = 24

15. If ‘÷’ stands for ‘division’, ‘-’ stands for ‘addition’, ‘×’ stands for ‘subtraction’ and ‘+’ stands for ‘multiplication’, then what will be the value of the following expression? [RRB NTPC 09/02/2021 (Morning)]

[{(15 × 10) − (3/5)} + (12 − 8)]/1

Correct Answer: (a) 1
Solution:

= [{(15 × 10) - (3/5)} + (12 - 8)]/1
= [{(15 - 10) + (3 × 5)} ÷ (12 + 8)] × 1
= 1

16. If ‘÷’ stands for addition, ‘×’ stands for subtraction, ‘+’ stands for division and ‘-’ stands for multiplication, then which of the following equations is correct? [RRB NTPC 09/02/2021 (Evening)]

Correct Answer: (a) 20 ÷ 12 + 6 × 5 - 2 = 12
Solution:

This type of question uses hit and trial method. solving option(a),
Given: 20 ÷ 12 + 6 × 5 - 2
After change the sign,
= 20 + 12 ÷ 6 - 5 × 2 = 20 + 2 - 10
= 22 - 10 = 12 = RHS

17. If ‘+’ means ‘divided’, ‘-’ means ‘add’, ‘×’ means ‘minus’, what will be the value of the following expression? [RRB NTPC 10/02/2021 (Morning)]

{6 - (2/7) + (4/5)}

Correct Answer: (d) 89/14
Solution:

18. If the following equation has to be balanced, then the signs in which of the following options will be used in the same sequence? [RRB NTPC 10/02/2021 (Evening)]

65, 5, 25 = 190

Correct Answer: (d) +, ×
Solution:

65, 5, 25 = 190
After going through options, we find that option (d) satisfies the equation.
65 + 5 × 25 = 190 ⇒ 65 + 125 = 190
190 = 190 (LHS = RHS)

19. If ‘×’ means ‘-’, ‘÷’ means ‘+’, ‘-’ means ‘÷’ and ‘+’ means ‘×’, then what is value of 40 × 5 + 10 - 2 ÷ 8? [RRB NTPC 10/02/2021 (Evening)]

Correct Answer: (c) 23
Solution:

40 × 5 + 10 - 2 ÷ 8
After changing the signs,
= 40 - 5 × 10 ÷ 2 + 8 = 40 - 25 + 8
= 40 - 25 + 8 = 48 - 25 = 23

20. Which amongst the given option could be the value of the expression 2 + 2 × 2 - 3 ÷ 3 × 3 - 4 × 4 ÷ 4 = ? [RRB NTPC 12/02/2021 (Morning)]

Correct Answer: (d) -1
Solution:

2 + 2 × 2 - 3 ÷ 3 × 3 - 4 × 4 ÷ 4 = -1