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A and B can do a job in 6 and 12 days respectively. They began the work together but A leaves after 3 days. Then the total number of days needed for the completion of the work is :
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- 4 days
- 5 days
- 6 days
- 9 days
Correct Option: C
| A’s one day’s work = | 6 |
| B’s one day’s work = | 12 |
(A + B)’s one day’s work
| = | + | = | = | |||||
| 6 | 12 | 12 | 4 |
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| Remaining work = 1 - | = | |||
| 4 | 4 |
∴ Total required number of days
| = | × | + 3 = 3 + 3 = 6 days | ||
| 4 | 1 |
Aliter : Using Rule 20,
Here, m = 6, n= 12, and p = 3
Time taken by B
| = | m |
| = | 6 |
| = | = 3 days | 6 |
∴ Total number of days taken to finish the works = 6 days
