Multiple choice

At their usual efficiency levels, A and B together finish a task in 12 days. If A had worked half as efficiently as she usually does, and B had worked thrice as efficiently as he usually does, the task would have been completed in 9 days. How many days would A take to finish the task if she works alone at her usual efficiency? A और B अपनी कार्यक्षमता से 12 दिनों में कार्य समाप्त आकर लेते है। यदि A अपनी कार्यक्षमता के आधे और B अपनी कार्यक्षमता के टीम गुने से कार्य करे तब वह साथ में 9 दिनों में कार्य पूरा करेंगे। तो बताइये A अकेला अपनी कार्यक्षमता से कार्य को कितने समय में पूरा करेगा?

  1. 24 days

  2. 18 days

  3. 12 days

  4. 36 days

  5. None of these इनमे से कोई नही
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let A's usual efficiency = a, B's usual efficiency = b. Total work = 12(a + b). With changed efficiencies: A works at 0.5a, B works at 3b. They finish in 9 days: 9(0.5a + 3b) = 12(a + b). Simplifying: 4.5a + 27b = 12a + 12b, giving 15b = 7.5a, so a = 2b. Total work = 12(a + 2a) = 36a. Time for A alone = 36a/a = 36 days. Wait, let me recalculate: If a = 2b, then original: 12(2b + b) = 36b. Changed: 9(0.5 × 2b + 3b) = 9(b + 3b) = 36b. This matches. A alone at efficiency 2b completes 36b work in 36b/2b = 18 days.

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