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Working 5 hours a day, A can complete a piece of work in 8 days and working 6 hours a day, B can complete the same work in 10 days. Working 8 hours a day, they both can complete the work in:1. 4 days2. 5.4 days3. 4.5 days4. 3 days |
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Answer» Correct Answer - Option 4 : 3 days Given: 'A' can complete a work in 8 days working 5 hours a day 'B' can complete a work in 10 days working 6 hours a day Concept used: If a person works in n days working y hours a day, then One day work by that person is 1/ny part of total work Calculation: One day work by A = 1/(8 × 5) ⇒ One day work by A = 1/40 And one day work by B = 1/(10 × 6) ⇒ one day work by B = 1/60 One day work by both A and B = one day work by A + one-day work by B ⇒ 1/(A +B) = (1/40) + (1/60) ⇒ 1/(A +B) = (3 + 2)/120 ⇒ 1/(A +B) = 5/120 ⇒ (A +B) one day work = 1/24 part of one work Then one work will be done by both A and B in 24 days Working 8 hrs a day Both A and B can complete a work = 24/8 ⇒ Working 8 hrs a day Both A and B can complete a work = 3 days ∴ Working 8 hrs a day Both A and B can complete a work in 3 days. |
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