A) 6 : 15pm
B) 7 : 12pm
C) 8 : 12pm
D) 8 : 35pm
Correct Answer: B
Solution :
[b] Let the cistern be emptied in x h after 3 pm Work done by A in x h, by B in \[(x-1)\,h\]and by C in \[(x-3)\,h=0\] \[\Rightarrow \] \[\frac{x}{3}+\frac{x-1}{4}-(x-2)=0\] \[\Rightarrow \] \[4x+3\,(x-1)-12\,(x-2)=0\] \[\Rightarrow \] \[5x=21\] \[\Rightarrow \] \[x=4\,h\,12\min \] Required time is 7 : 12 pm. |
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