If 5 liters of paint covers 100 square meters, how many square meters will 8 liters cover?

Appeared in: RML PRE 2025

Explanation

The problem demonstrates a direct proportion: as the volume of paint increases, the area covered increases at a constant rate.
The first step is to find the unit rate by dividing the total area by the total volume of paint: 100 sqm / 5 liters = 20 sqm per liter.
The second step is to multiply this unit rate by the new volume to find the new area: 20 sqm/liter * 8 liters = 160 sqm.

Option A: This value is too low. It would be the area covered by 6 liters of paint (6 x 20), not 8.
Option B: This value is incorrect. It represents the area that would be covered by 7.5 liters of paint (7.5 x 20).
Option D: This value is too high. It represents the area that would be covered by 9 liters of paint (9 x 20).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Direct Proportion and Unitary Method as background academic context rather than a clinical decision trigger.
While this is a general math question, the underlying skill (unitary method) is critical for safe nursing practice, especially in medication administration and IV therapy.
For example, if a vial contains 500 mg of a drug in 5 mL, a nurse uses the unitary method to calculate that 1 mL contains 100 mg. This is essential for drawing up the correct dose.
What if the paint coverage was not linear (e.g., the first coat uses more paint than the second)? The unitary method would no longer apply, and a different calculation model would be needed. Similarly, in pharmacology, some drug effects are not linear, which is why understanding concepts like half-life is also important.

How to Approach the Question

First, identify the relationship between the two quantities (liters of paint and square meters). In this case, it's a direct proportion.
Next, determine the value of a single unit. This is the 'unitary' part of the method. Calculate how many square meters 1 liter of paint covers.
Use the value of the single unit to find the value for the required number of units. Multiply the area covered by 1 liter by the new quantity (8 liters).
Finally, check your answer against the options provided and quickly verify the other options to ensure your calculation is sound.

Concept Tested & Keywords

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Practise the full RML PRE 2025

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