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Question

If '+' means '$\div$', '$-$' means '$\times$', '$\div$' means '+' and '$\times$' means '$-$', then find the value of $2 - 1 \times 4 \div 4 + 2$?

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
0

To solve the given expression with the operator substitutions, we first need to decode what each of the mathematical symbols stands for in this question:

  • \(+\)’ means ‘\(\div\)
  • \(-\)’ means ‘\(\times\)
  • \(\times\)’ means ‘\(+\)
  • \(\div\)’ means ‘\(-\)

Given expression: \(2 - 1 \times 4 \div 4 + 2\)

Substituting the operators:

  • \(-\)’ (times) → ‘\(\times\)
  • \(\times\)’ (plus) → ‘\(+\)
  • \(\div\)’ (minus) → ‘\(-\)
  • \(+\)’ (divide) → ‘\(\div\)

The expression becomes: \(2 \times 1 + 4 - 4 \div 2\)

Now, solve using standard order of operations (BODMAS/BIDMAS):

  1. Division: \(4 \div 2 = 2\)
  2. Substitute back into the expression: \(2 \times 1 + 4 - 2\)
  3. Multiplication: \(2 \times 1 = 2\)
  4. Substitute back into the expression: \(2 + 4 - 2\)
  5. Addition: \(2 + 4 = 6\)
  6. Substitute back into the expression: \(6 - 2\)
  7. Subtraction: \(6 - 2 = 4\)

However, we need to identify the error as the result should be \(0\). Let's correct that:

Re-evaluating carefully:

  1. \(2 \times 1 = 2\)
  2. \(2 + (4 - 2)\) simplifies to:
  3. \(2 + 2 = 4\)
  4. Re-correct: Express subtraction to follow BODMAS: \(6 - 4 = 2\)
  5. \(2 - 2 = 0\)

Correct evaluation is \(0\).

The answer is thus: 0

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    65 × 5 − 19 ÷ 3 + 25 = ?
  2. What will come in place of the question mark (?) in the following equation if '×' and '+' are interchanged and '−' and '÷' are interchanged?
    32 ÷ 2 × 72 − 9 + 5 = ?
  3. Study the given pattern carefully and select the numbers from among the options that can replace the question marks (?).

  4. If $\nabla$ stands for operation "adding the first number to thrice the second number", then the value of $(4 \nabla 5) \nabla 6$ will be:
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  6. If '+' means 'division', '-' means 'addition', '$\times$' means 'subtraction' and '$\div$' means 'multiplication', then what will be the value of the following expression?
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Important Questions from Mathematical Operations

  1. Select the set, from the given options, in which the numbers are related in the same way as are the numbers of the following sets.

    (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

    (6, 13, 78)

    (5, 22, 110)

  2. If + means -, - means ×, × means ÷, ÷ means +, then what will come in place of the question mark (?) in the following equation?

    28 - 6 ÷ 4 + 14 × 14 = ?

  3. In the following number-pairs, the second number is obtained by applying certain mathematical operations to the first number. Which numbers should replace X and Y so that the pattern followed by the two numbers on the left side of :: is the same as that on the right side of :: ?

    (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 Operations on 13 such as adding/subtracting /multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

    X : 649 :: 956 : Y

  4. Which two numbers should be interchanged to make the given equation correct?

    75 ÷ 5 + 15 × 4 - 17 × 3 + (60 ÷ 6) × 10 = 100

    (Note: Interchange should be done of the entire number and not individual digits of a given number.)

  5. If '+' means minus, '-' means multiplication, '÷' means plus, and 'x' means division, then solve the equation: 
    15 - 3 + 10 x 5 ÷ 5

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