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Question

If '$+$' means 'subtraction', '$\div$' means 'addition', '$-$' means 'multiplication' and '$\times$' means 'division', then what is the value of $(8 + 2 - 19) - (4 + 27 \times 3)$?

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
150

Symbol Substitution Logic

The problem requires substituting mathematical symbols based on a given code and then evaluating the expression using the standard order of operations (BODMAS/PEMDAS).

Symbol Mapping

First, let's establish the new meaning for each symbol as defined:

  • '$+$' is replaced by '$-$' (subtraction).
  • '$\div$' is replaced by '$+$' (addition).
  • '$-$' is replaced by '$\times$' (multiplication).
  • '$\times$' is replaced by '$\div$' (division).

Rewriting the Expression

The original expression is: $(8 + 2 - 19) - (4 + 27 \times 3)$

Now, apply the symbol substitutions to the entire expression:

  • The '+' inside the first parenthesis becomes '-'.
  • The '-' inside the first parenthesis becomes '$\times$'.
  • The main '-' operator connecting the two parentheses becomes '$\times$'.
  • The '+' inside the second parenthesis becomes '-'.
  • The '$\times$' inside the second parenthesis becomes '$\div$'.

The transformed expression is: $(8 - 2 \times 19) \times (4 - 27 \div 3)$

Step-by-Step Evaluation

Evaluate the expression using the order of operations (Parentheses/Brackets, Orders/Exponents, Division and Multiplication (left-to-right), Addition and Subtraction (left-to-right)).

  1. Solve the first parenthesis: $(8 - 2 \times 19)$
    • Perform multiplication first: $2 \times 19 = 38$.
    • Perform subtraction: $8 - 38 = -30$.
  2. Solve the second parenthesis: $(4 - 27 \div 3)$
    • Perform division first: $27 \div 3 = 9$.
    • Perform subtraction: $4 - 9 = -5$.
  3. Perform the final operation: The expression is now $(-30) \times (-5)$.
    • Multiply the results: $(-30) \times (-5) = 150$.

Final Result

The value of the expression after applying the symbol substitutions and evaluating according to the order of operations is 150.

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Important Questions from Mathematical Operations

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    21 × 8 – 18 + (64 ÷ 2) + 32 = 64

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    9 × 1 ÷ 3 + 8 – 7 = 12 ÷ 3 + 2 × 33 – 13

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    (6, 13, 78)

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    X : 649 :: 956 : Y

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