A) 40 min
B) 1 h 20 min
C) 1 h
D) 30 min
Correct Answer: C
Solution :
| [c] Let usual speed of a man is V and time is t h. By the formula, \[{{V}_{1}}\,{{t}_{1}}={{V}_{2}}\,{{t}_{2}}\] \[V\,t=1\frac{1}{2}V\,\left( t-\frac{20}{60} \right)\] \[\Rightarrow \] \[t=\frac{3}{2}\,\left( t-\frac{1}{3} \right)\] \[\Rightarrow \] \[\frac{3}{2}t-t=\frac{1}{2}\] \[\Rightarrow \] \[t=1\,h\] Hence, the time taken by the man to reach his office at his usual speed is 1 h. |
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