DSSSB - 29 August 2019 (Shift-1)
Reasoning
Hard
Which two numbers should be interchanged to make the below equation mathematically correct?
7 + 16 / 4 * 3 - 5 = 10
Appeared in: DSSSB - 29 August 2019 (Shift-1)
Explanation
- The correct answer involves interchanging the numbers 7 and 5.
- The new equation becomes:
5 + 16 / 4 * 3 - 7 = 10. - Following the BODMAS rule, first perform division:
16 / 4 = 4. - Next, perform multiplication:
4 * 3 = 12. - The equation simplifies to
5 + 12 - 7. - Finally, perform addition and subtraction from left to right:
17 - 7 = 10.
Why Other Options Were Wrong
- Option A: Interchanging 7 and 3 results in the equation
3 + 16 / 4 * 7 - 5. Following BODMAS, this evaluates to3 + 4 * 7 - 5 = 3 + 28 - 5 = 26, which is not 10. - Option B: Interchanging 3 and 5 results in the equation
7 + 16 / 4 * 5 - 3. Following BODMAS, this evaluates to7 + 4 * 5 - 3 = 7 + 20 - 3 = 24, which is not 10. - Option D: Interchanging 4 and 5 results in the equation
7 + 16 / 5 * 3 - 4. Following BODMAS, this evaluates to7 + 3.2 * 3 - 4 = 7 + 9.6 - 4 = 12.6, which is not 10.
Related Visual
Clinical Relevance
- Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Order of Operations (BODMAS/PEMDAS) as background academic context rather than a clinical decision trigger.
- While not a clinical question, basic numeracy is a fundamental skill for nurses.
- Accurate mathematical calculation is critical for patient safety in tasks like medication dosage calculation, IV fluid rate administration, and titrating drips.
- A simple error in the order of operations during a dosage calculation could lead to a significant medication error, causing harm to the patient.
How to Approach the Question
- First, understand the question. You need to find which pair of numbers to swap to make the equation true.
- Recall the order of mathematical operations using the acronym BODMAS (Brackets, Orders, Division, Multiplication, Addition, Subtraction).
- Evaluate the original equation (
7 + 16 / 4 * 3 - 5) to confirm it is incorrect. The result is 14, not 10. - Systematically test each option provided. For each option, swap the two numbers in the original equation.
- Recalculate the value of the new equation using the BODMAS rule.
- The correct option is the one that makes the equation's value equal to 10.
Concept Tested & Keywords
- Concept Tested: Order of Operations (BODMAS/PEMDAS)
- Stem keywords: interchanged, equation, mathematically correct
- Lead-in keywords: Which two numbers
- Negative lead-in flag: false
Question ID
Q-Hr_ctSLahKW1Q8gRMdj_
Practise the full DSSSB - 29 August 2019 (Shift-1)
Attempt every question from this paper in a timed mock, then review the full solution for each one.
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