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A takes 10 days less than the time taken by B to finish a piece of work. If both A and B can do it in 12 days, then the time taken by B alone to finish the work is
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- 30 days
- 27 days
- 20 days
- 25 days
Correct Option: A
Using Rule 2,
Let time taken by B in completing the work = x days
∴ Time taken by A = (x – 10) days
| ∴ | + | = | ||||
| x | x - 10 | 12 |
| ⇒ | = | |||
| x(x - 10) | 12 |
⇒ 24x – 120 = x2 – 10x
⇒ x2 – 34x + 120 = 0
⇒ x2 – 30x – 4x + 120 = 0
⇒ x (x – 30) – 4 (x – 30) = 0
⇒ (x – 4) (x – 30) = 0
⇒ x = 30 because x ≠ 4
