A) 6 hrs
B) 62 hrs
C) 7 hrs
D) \[7\frac{1}{2}\]hrs.
Correct Answer: C
Solution :
[c](A+B)'s 1 hour work \[=\left( \frac{1}{12}+\frac{1}{15} \right)=\frac{3}{20}\] (A+ C)'s 1 hour work \[=\left( \frac{1}{12}+\frac{1}{20} \right)=\frac{2}{15}\] Part filled in 2 hours \[=\frac{3}{20}+\frac{2}{15}=\frac{17}{60}\] \[\therefore \] Part filled in 6 hours \[=3\times \frac{17}{60}=\frac{17}{20}\] Remaing part to be filled \[=1-\frac{17}{20}=\frac{3}{20}\] This is now filled by (A + B) in 7th hour. Total time = 7 hours.You need to login to perform this action.
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