Inverse men–days relation: 36 men can complete a piece of work in 18 days. In how many days will 27 men complete the same work (same rate)?
Aptitude
Unitary Method
Difficulty: Easy
Choose an option
Answer
Correct Answer: 24
Explanation
Introduction / Context:With constant productivity, work done equals men * days. For a fixed job, men and days are inversely proportional. Reducing workers increases the required days proportionally.Given Data / Assumptions:
- 36 men finish in 18 days.
- Find days for 27 men at same rate.
Concept / Approach:Use men1 * days1 = men2 * days2. Solve for days2 with the given numbers.Step-by-Step Solution:
36 * 18 = 27 * days2days2 = (36 * 18) / 27 = (36/27) * 18 = (4/3) * 18 = 24Verification / Alternative check:Total man-days = 36 * 18 = 648. With 27 men, days = 648 / 27 = 24. Same result.
Why Other Options Are Wrong:
- 23, 34, 39: Do not preserve the constant man-days 648 for the fixed job.
Common Pitfalls:Using direct instead of inverse proportion between men and days for fixed work. Keep the product men * days constant for the given job.
Final Answer:
24