| Walking at \[\frac{3}{4}th\] of his usual speed, a man reaches his office 20 min late. What is the time taken by him to reach the office at his usual speed? |
A) 80 min
B) 70 min
C) 60 min
D) 50 min
Correct Answer: C
Solution :
| Let usual speed of the man be x km/h. |
| Then, new speed \[=\frac{3}{4}x\] |
| Let D is the distance to cover. |
| \[\frac{D}{\frac{3}{4}x}-\frac{D}{x}=\frac{20}{60}\]\[\Rightarrow \]\[\frac{4D}{3x}-\frac{D}{x}=\frac{20}{60}\] |
| \[\Rightarrow \] \[\frac{D}{3x}=\frac{1}{3}\]\[\Rightarrow \]\[\frac{D}{x}=1h=60\,\text{min}\] |
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