Multiple choice

A, B working together can finish a work in 48 days and C and D working together can finish the same work in 72 days. If A, B and C worked together for 40 days then C leave the work and remaining work finished by A and B together in 8 days. Find in how many days D alone can finish the whole work? A,B मिलकर 48 दिनों में एक काम पूरा कर सकते है और C,D मिलकर 72 दिनों में उसी काम को समाप्त कर सकते है। यदि A,B और C 40 दिनों के लिए एक साथ काम करते हैं,उसके बाद C काम छोड़ देता है और बचे हुए कार्य को A और B 8 दिनों में काम समाप्त कर देते है। तो D अकेले पूरे कार्य को कितने दिनों में समाप्त कर सकता है?

  1. 144

  2. 120

  3. 72

  4. 96
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let A+B rate = 1/48 work per day. Let C+D rate = 1/72 work per day. Work done in first 40 days by A+B+C = 40(1/48 + c) = 40/48 + 40c. Remaining work = 1 - 40/48 - 40c = 8/48 - 40c. A+B finish this in 8 days: 8(1/48) = 8/48 - 40c. This gives c = 0, meaning C contributed nothing - which is unrealistic. Alternative interpretation: the given answer C (72 days) equals the C+D combined rate, suggesting D alone matches the pair's rate. The problem likely has inconsistent data or expects recognizing D = C+D rate.

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