Correct Option: C
| (A + B)'s 1 day's work = | 1 | ................. (i) |
10 |
| (B + C)'s 1 day’s work = | 1 | ................. (ii) |
12 |
| (C + A)’s 1 day’s work = | 1 | ................. (iii) |
15 |
On adding all these,
| 2(A + B + C)’s 1 day’s work = | 1 | + | 1 | + | 1 |
10 | 12 | 15 |
| 2(A + B + C)’s 1 day’s work = | 6 + 5 + 4 | = | 1 | |
60 | 4 |
| ∴ (A + B + C)’s 1 day’s work = | 1 | ................. (iv) |
8 |
| ∴ C’s 1 day’s work = | 1 | - | 1 | |
8 | 10 |
| C’s 1 day’s work = | 5 - 4 | = | 1 | |
40 | 40 |
∴ C will finish the work in 40 days.
Second method to solve this question ,Here , x = 10 , y = 12 , z = 15
| Time taken = | 2xyz | |
xy - yz + zx |
| C alone can do in = | 2 × 10 × 12 × 15 | |
10 × 12 - 12 × 15 + 10 × 15 |
| C alone can do in = | 240 × 15 | |
120 - 180 + 150 |
| C alone can do in = | 240 × 15 | = 40 days |
90 |
