A piece of work can be done by 6 men and 5 boys in 6 days. 3 men and 4 boys can complete the same work in 10 days. In how many days can it be done by 9 men and 6 boys? 6 व्यक्ति और 5 लड़के काम के एक भाग को 6 दिन में पूरा करते है। 3 व्यक्ति और 4 लड़के 10 दिन में इसी कार्य को पूरा करते है तो 9 व्यक्ति और 6 लड़के कार्य कितने दिनों में पूरा करेगें?

Let m = work done by 1 man in 1 day, b = work done by 1 boy in 1 day. From first condition: 6m + 5b = 1/6. From second condition: 3m + 4b = 1/10. Multiplying second equation by 2: 6m + 8b = 1/5. Subtracting first: 3b = 1/5 - 1/6 = 1/30, so b = 1/90. Then 6m = 1/6 - 5/90 = 15/90 - 5/90 = 10/90, giving m = 1/54. For 9 men and 6 boys: 9m + 6b = 9/54 + 6/90 = 1/6 + 1/15 = 5/30 + 2/30 = 7/30. Time = 1/(7/30) = 30/7 ≈ 4.3 days (not in options).