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A and B can separately complete a piece of work in 20 days and 30 days respectively. They worked together for some time, then B left the work. If A completed the rest of the work in 10 days, then B worked for
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- 6 days
- 8 days
- 12 days
- 16 days
Correct Option: A
Let A and B worked together for x days
According to the question,
Part of work done by A for (x + 10) days + part of work done by B for x days = 1
| ⇒ | + | = 1 | ||
| 20 | 30 |
| ⇒ | = 1 | |
| 60 |
⇒ 5x + 30 = 60
⇒ 5x = 30
| ⇒ | = 6 days | |
| 5 |
Aliter :
Using Rule 20,
Here, m =20, n= 30,
π = x and time taken by A alone = 10
mn p m n n - + ()
| ⇒ 10 = | |
| n |
| 10 = | |
| 30 |
= 600 – x 50
50x = 300 x = 6
⇒ B worked for 6 days
