A) 10 min 20 s
B) 11 min 45 s
C) 12 min 30 s
D) 14 min 40 s
Correct Answer: D
Solution :
| [d] Part filled by both in 4 min \[=4\times \left( \frac{1}{15}+\frac{1}{20} \right)=\left( 4\times \frac{7}{60} \right)=\frac{7}{15}\] Part unfilled\[=\left( 1-\frac{7}{15} \right)=\frac{8}{15}\] \[\frac{1}{20}\]part is filled by B in 1 min. \[\frac{8}{15}\]part is filled by B in\[\left( 20\times \frac{8}{15} \right)\min \] \[=\frac{32}{3}\min =10\min 40\,s\] Total time taken = (4 min + 10 min 40 s) = 14 min 40 s |
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