A) 36
B) 12
C) 18
D) 9
Correct Answer: A
Solution :
[a] Let A takes n days to complete a work then, time taken by \[B=2n\] \[(A+B')\,1\]day work \[=\frac{1}{12}\] \[\Rightarrow \] \[\frac{1}{n}+\frac{1}{2n}=\frac{1}{12}\] \[\Rightarrow \] \[\frac{2+1}{2n}=\frac{1}{12}\] \[\therefore \] \[n=\frac{12\times 3}{2}=18\] \[\therefore \] Time taken by B alone \[=2n=2\times 18\] = 36 days |
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