0.002 x 0.5 = ?

Appeared in: AIIMS Rishikesh & Jodhpur NO - 2017

Explanation

To multiply decimals, first multiply the numbers without considering the decimal points (2 x 5 = 10).
Next, count the total number of decimal places in the numbers being multiplied. In this case, 0.002 has three decimal places, and 0.5 has one, for a total of four decimal places.
Place the decimal point in the product (10) so that it has the total number of decimal places counted. Moving the decimal four places to the left in '10' gives 0.0010.
Finally, simplify the result by removing any trailing zeros, which gives 0.001.

Option A: This result implies a total of five decimal places, which is incorrect. The sum of decimal places is 3 (from 0.002) + 1 (from 0.5) = 4.
Option C: This result implies a total of three decimal places, which is incorrect. This error might occur if the decimal place from 0.5 was not counted.
Option D: This result implies a total of two decimal places, which is incorrect. This is a significant miscalculation of the required decimal places.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Multiplication of decimal numbers as background academic context rather than a clinical decision trigger.
Accurate mathematical skills are non-negotiable in nursing for safe medication administration. Misplacing a decimal point is one of the most common causes of medication errors.
A tenfold error in dosage (e.g., administering 1.0 mg instead of 0.1 mg) can have catastrophic consequences for the patient, including toxicity or death.
What if? If the prescription was for 0.02 x 0.5, the answer would be 0.01. This highlights how a single zero's position dramatically changes the outcome, reinforcing the need for careful attention to detail in all calculations.

How to Approach the Question

First, identify the mathematical operation required, which is multiplication.
Ignore the decimal points and multiply the whole numbers: 2 times 5 equals 10.
Count the total number of digits to the right of the decimal point in both of the original numbers. '0.002' has 3, and '0.5' has 1, for a total of 4.
Take the product from step 2 (which is 10) and place the decimal point so there are 4 digits to its right. You will need to add leading zeros: 0.0010.
Simplify the result by removing any trailing zeros. 0.0010 becomes 0.001.
Compare your final answer with the given options to find the correct one.

Concept Tested & Keywords

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E6 Nursing Fundamentals Taylor p. 848-850

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