Find out the solution: 15.5 x 3?

Appeared in: SGPGI Nursing Officer-2022

Explanation

The product of 15.5 and 3 is correctly calculated as 46.5.
One way to solve this is by breaking the number down: (15 × 3) + (0.5 × 3).
This simplifies to 45 + 1.5, which equals 46.5.
Alternatively, multiply 155 by 3 to get 465, then place the decimal point one place from the right to account for the decimal in 15.5, resulting in 46.5.

Option B: This is an incorrect calculation. It might arise from an error in adding the partial products, such as adding 0.5 instead of 1.5 to 45.
Option C: This is a simple calculation error. There is no standard multiplication mistake that leads directly to this answer.
Option D: This answer is obtained by ignoring the decimal part (0.5) of 15.5 and only multiplying the whole number part (15 × 3 = 45).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Multiplication of a decimal number by a whole number as background academic context rather than a clinical decision trigger.
Accurate calculation is a fundamental skill for nurses, especially for medication dosage calculations, where even a small error can have significant consequences for patient safety.
What if? - If a nurse needed to administer 3 doses of a medication that comes in 15.5 mg tablets, a miscalculation like ignoring the decimal (getting 45 mg instead of 46.5 mg) would result in underdosing the patient, potentially making the treatment ineffective.

How to Approach the Question

Identify the mathematical operation required, which is multiplication.
Note the numbers involved: one is a decimal (15.5) and the other is a whole number (3).
Choose a calculation method. A simple method is to first ignore the decimal and multiply 155 by 3, which equals 465.
Count the number of digits after the decimal point in the original number(s). In this case, there is one digit after the decimal in 15.5.
Place the decimal point in your result (465) so that it has the same number of decimal places. This gives you 46.5.
Finally, compare your result with the given options to select the correct answer.

Concept Tested & Keywords

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