After 15 years, a man will be just 4 times as old as he was 15 years ago. What is his present age?

Appeared in: NHM MP Staff Nurse - 2015

Explanation

Let the present age be 'x'. The problem can be translated into the equation: (x + 15) = 4 * (x - 15).
Distributing the 4 on the right side gives: x + 15 = 4x - 60.
Rearranging the terms to solve for x results in: 4x - x = 15 + 60, which simplifies to 3x = 75.
Dividing both sides by 3 yields x = 25. Therefore, the man's present age is 25 years.

Option A: If the present age is 10, his age 15 years ago would be 10 - 15 = -5 years, which is not possible.
Option B: If the present age is 20, his age after 15 years is 35, and his age 15 years ago was 5. 35 is 7 times 5, not 4 times.
Option C: If the present age is 15, his age 15 years ago was 0. The equation becomes 30 = 4 * 0, which is false (30 is not equal to 0).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Solving linear equations from word problems as background academic context rather than a clinical decision trigger.
While this is a general aptitude question, the underlying skill of logical reasoning is crucial in nursing.
Nurses use mathematical skills daily for tasks like calculating medication dosages, titrating IV drips, and interpreting patient data charts, where precision is vital for patient safety.
What if the problem stated his age would be 3 times as old? The equation would change to x + 15 = 3(x - 15). Solving this gives 2x = 60, so x = 30 years. This demonstrates how a small change in the problem's parameters leads to a different outcome.

How to Approach the Question

First, carefully read the question to identify the unknown quantity. Here, it's the 'present age'.
Assign a variable, such as 'x', to represent this unknown quantity.
Translate the phrases in the word problem into mathematical expressions. 'After 15 years' becomes 'x + 15', and '15 years ago' becomes 'x - 15'.
Formulate an equation based on the relationship described: (x + 15) = 4 * (x - 15).
Solve the algebraic equation for 'x' using standard methods of rearranging and simplifying.
Finally, check your answer by substituting the value of 'x' back into the original problem statement to ensure it holds true.

Concept Tested & Keywords

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Practise the full NHM MP Staff Nurse - 2015

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