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

RRB Staff Nurse Mumbai-2015

Non Nursing Subjects

Hard

Appeared in: RRB Staff Nurse Mumbai-2015

Explanation

The problem requires setting up an algebraic equation to find an unknown value (present age).
Let the present age be 'x'. The age 15 years in the future is (x + 15), and the age 15 years in the past was (x - 15).
The relationship described is 'future age = 4 * past age', which gives the equation: x + 15 = 4 * (x - 15).
Solving the equation begins by distributing the 4: x + 15 = 4x - 60.
Rearranging the terms to isolate x gives 3x = 75.
Dividing by 3 yields the final answer, x = 25.

Option A: If the present age is 10, the age 15 years ago would be 10 - 15 = -5. Age cannot be a negative value, so this option is logically impossible.
Option B: If the present age is 15, the age 15 years ago was 15 - 15 = 0. The age 15 years hence would be 15 + 15 = 30. According to the problem, 30 should be 4 times 0, which is incorrect (30 is not equal to 0).
Option C: If the present age is 20, the age 15 years ago was 20 - 15 = 5. The age 15 years hence would be 20 + 15 = 35. According to the problem, 35 should be 4 times 5. However, 4 * 5 = 20, not 35.

Visual 1: Infographic - A step-by-step guide on how to translate word problems into algebraic equations. This would show how to identify the unknown (variable 'x'), translate phrases like 'years hence' and 'years ago' into expressions, and set up the final equation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Solving age-related word problems using linear equations as background academic context rather than a clinical decision trigger.
While not a direct clinical skill, proficiency in logical reasoning and problem-solving, as tested in aptitude questions, is crucial for nurses.
Nurses constantly use similar logical processes for critical tasks like drug dosage calculations, interpreting trends in lab values, and adjusting patient care plans based on changing data.
This type of analytical thinking helps in making quick, accurate decisions in high-pressure clinical environments.

How to Approach the Question

First, carefully read the problem to identify the unknown quantity. Here, it's the 'man's present age'.
Assign a variable to this unknown. Let 'x' represent the present age.
Translate the time-based phrases into algebraic expressions: '15 years hence' becomes (x + 15), and '15 years ago' becomes (x - 15).
Formulate an equation based on the relationship described. The phrase '4 times as old as' means you must multiply one expression by 4 to make it equal to the other: (x + 15) = 4 * (x - 15).
Solve the resulting linear equation for the variable 'x' using standard algebraic steps.
Finally, verify your answer by plugging the value of 'x' back into the original problem's conditions to ensure it makes sense and is correct.

Concept Tested & Keywords

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