Correct Option: C
| (A + B)’s 1 day’s work = | 1 | |
| 20 |
| (B + C)’s 1 day’s work = | 1 | |
| 10 |
| (C + A)’s 1 day’s work = | 1 | |
| 12 |
On adding all three,
| 2 (A + B + C)’s 1 day’s work = | 1 | + | 1 | + | 1 |
20 | 10 | 12 |
| 2 (A + B + C)’s 1 day’s work = | 3 + 6 + 5 | |
| 60 |
| 2 (A + B + C)’s 1 day’s work = | 14 | = | 7 | |
60 | 30 |
| ∴ (A + B + C)’s 1 day’s work = | 7 | |
| 60 |
| ∴ Hence, the work will be completed in | 60 | = 8 | 4 | days |
7 | 7 |
Second method to solve this question ,Here , x = 20 , y = 10 , z = 12
| Time taken = | 2xyz | |
| xy + yz + zx |
| Time taken = | 2 × 20 × 10 × 12 | |
| 20 × 10 + 10 × 12 + 12 × 20 |
| Time taken = | 4800 | |
| 200 + 120 + 240 |
| Time taken = | 60 | = 8 | 4 | days |
7 | 7 |
