If '+' means '-', '÷' means '×', '×' means '+' and '-' means '÷', then what will be the value of the following expression?
49 - 7 + 7 × 49 ÷ 7

Appeared in: UP NHM CHO 7 Sept 2022(shift-1st)

Explanation

The core task is to first replace the operators in the expression according to the given rules and then solve it using the correct order of operations (BODMAS).
The original expression 49 - 7 + 7 × 49 ÷ 7 transforms into 49 ÷ 7 - 7 + 49 × 7 after substitution.
Following BODMAS, we first perform division (49 ÷ 7 = 7) and multiplication (49 × 7 = 343).
The expression simplifies to 7 - 7 + 343.
Finally, performing subtraction and addition from left to right (7 - 7 = 0, then 0 + 343 = 343) yields the correct answer.

Option A: This result is incorrect and likely stems from a combination of errors in substitution and calculation, possibly involving incorrect handling of signs.
Option B: This value (91) is obtained if the original expression is solved without applying the operator substitution rules. Calculation: 49 - 7 + (7 × 49 ÷ 7) = 42 + 49 = 91.
Option C: This is an incorrect value that likely arises from significant miscalculation or not following the BODMAS rule after making the substitutions.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mathematical Reasoning with Operator Substitution as background academic context rather than a clinical decision trigger.
This question tests logical and sequential reasoning, a critical skill for nurses.
Nurses must follow multi-step procedures and protocols in a precise order, similar to applying the BODMAS rule in mathematics. An error in sequence can impact patient safety.
This skill is essential for tasks like calculating drug dosages, where substituting values into a formula and performing calculations in the correct order is paramount.

How to Approach the Question

Step 1: Carefully read the question to identify the specific substitution rule for each mathematical operator.
Step 2: Create a simple table or list to keep track of the changes (e.g., '+' → '-', '÷' → '×').
Step 3: Rewrite the entire mathematical expression, replacing each original operator with its new, substituted operator.
Step 4: Apply the BODMAS rule (Brackets, Orders, Division, Multiplication, Addition, Subtraction) to the newly formed expression.
Step 5: Perform the calculations sequentially according to the BODMAS rule to arrive at the final value.
Step 6: Compare your final answer with the given options to select the correct one.

Concept Tested & Keywords

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Practise the full UP NHM CHO 7 Sept 2022(shift-1st)

Attempt every question from this paper in a timed mock, then review the full solution for each one.