Difficulty: Hard
Correct Answer: ₹ 2700
Explanation:
Introduction / Context:
Here, not all workers stay for the full duration. We must first determine the total project duration from the staggered participation, then compute each person’s actual work amount. Finally, allocate the fixed ₹ 5400 proportional to these contributions. This mixes rate calculations with timeline reasoning.
Given Data / Assumptions:
Concept / Approach:
Let total duration = T days. Then total work equals: T/20 + (T − 2)/24 + (T − 5)/30 = 1. Solve for T. Then compute A’s work fraction = T/20 and multiply by ₹ 5400 to get A’s share.
Step-by-Step Solution:
T/20 + (T − 2)/24 + (T − 5)/30 = 1Use denominator 120: (6T) + 5(T − 2) + 4(T − 5) all over 120 = 1⇒ (6T + 5T − 10 + 4T − 20) / 120 = 1 ⇒ (15T − 30) / 120 = 115T − 30 = 120 ⇒ 15T = 150 ⇒ T = 10 daysA’s work = T/20 = 10/20 = 1/2 of the jobA’s share = 1/2 * ₹ 5400 = ₹ 2700
Verification / Alternative check:
Compute B and C: B’s work = (T − 2)/24 = 8/24 = 1/3; C’s work = (T − 5)/30 = 5/30 = 1/6. Sum = 1/2 + 1/3 + 1/6 = 1 — perfect balance.
Why Other Options Are Wrong:
₹ 540, ₹ 600 are too small; ₹ 1800 understates A’s half-share.
Common Pitfalls:
Assuming all worked for T days; ignoring the early departures; arithmetic errors when clearing denominators.
Final Answer:
₹ 2700
Discussion & Comments