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While working 7 hours a day, A alone can complete a piece of work in 6 days and B alone in 8 days. In what time would they complete it together, working 8 hours a day ?
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- 3 days
- 4 days
- 2.5 days
- 3.6 days
Correct Option: A
A alone can complete the work in 42 days working 1 hour daily. Similarly, B will take 56 days working 1 hour daily.
| A ’s 1 day’s work = | 42 |
| B ’s 1 day’s work = | 56 |
| (A + B) ’s 1 day’s work = | + | 42 | 56 |
| = | = | 168 | 168 |
| ∴ Time taken by (A + B) working 8 hours daily = | = 3 days | 7 × 8 |
Second method to solve this question ,
Here, h1 = 6 hours, h2 = 8 hours
d1 = 6 days, d2 = 8 days,
h = 8 hours
| Required Time = |  |  | × | 6 × 6 + 8 × 8 | 8 |
| Required Time = | × | 100 | 8 |
| Required Time = | = 2.88 ≈ 3 days | 100 × 8 |
