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A and B can do a piece of work in 72 days. B and C can do it in 120 days and A and C can do it in 90 days. A alone can do it in :
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- 120 days
- 130 days
- 150 days
- 100 days
Correct Option: A
(A + B)’s 1 day’s work
| = | ...........(i) | 72 |
(B + C)’s 1 day’s work
| = | ...........(ii) | 120 |
(C + A)’s 1 day’s work
| = | ...........(iii) | 90 |
On adding all three,
2 (A + B + C)’s 1 day’s work
| = | + | + | ||||
| 72 | 120 | 90 |
| = | = | = | ||||
| 360 | 360 | 30 |
∴ (A + B + C)’s 1 day’s work
| = | ...........(iv) | 60 |
∴ A’s 1 day’s work
= Equation (iv) – (ii),
| = | - | = | = | |||||
| 60 | 120 | 120 | 120 |
∴ Required time = 120 days
