| A does 20% less work than B. If A complete a piece of work in \[7\frac{1}{2}h,\] then B can do it in |
A) \[6\frac{1}{2}h\]
B) \[6\,\,h\]
C) \[5\frac{1}{2}h\]
D) \[5\,\,h\]
Correct Answer: B
Solution :
| Let the slower pipe fills a tank in \[x\,\,h,\]then faster pipe fills the tank in \[\frac{x}{3}h.\] |
| Now, \[\frac{1}{x}+\frac{1}{x/3}=\frac{1}{36}\times 60h\] |
| \[\Rightarrow \] \[\frac{1}{x}+\frac{3}{x}=\frac{60}{36}\] |
| \[\Rightarrow \] \[\frac{4}{x}=\frac{60}{36}\]\[\Rightarrow \]\[=\frac{12}{5}=2\,\,h\,\,24\min \] |
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