A) \[1\frac{1}{3}h\]
B) \[2\,h\]
C) \[1\frac{2}{3}h\]
D) \[2\frac{2}{3}h\]
Correct Answer: A
Solution :
| [a] Let the time taken by A be x h. Then, time taken by B \[=\left( x-\frac{20}{60} \right)\,h\] \[=\left( x-\frac{1}{3} \right)\,h\] Ratio of speeds = Inverse ratio of time taken. \[\therefore \] \[3:4=\left( x-\frac{1}{3} \right):x\] \[\Rightarrow \] \[\frac{3x-1}{3x}=\frac{3}{4}\] \[\Rightarrow \] \[12x-4=9x\] \[\Rightarrow \] \[3x=4\] \[\Rightarrow \] \[x=\frac{4}{3}\,h=1\frac{1}{3}\,h\] Required time \[=1\frac{1}{3}\,h\] |
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