| A 320 m long train moving with an average speed of 120 km/h crosses a platforms 24 s. A man crosses the same platform in 4 min. What is the speed (in m/s) of man? [BOB (PO) 2011] |
A) 2.4
B) 1.6
C) 2.2
D) 1.5
E) None of these
Correct Answer: E
Solution :
| Speed of train = 120 km/h |
| \[=\frac{120\times 5}{18}=\frac{100}{3}\,\,m/s\] |
| Let the length of the platform be x m. |
| Then, \[\frac{x+320}{\frac{100}{3}}=24\]\[\Rightarrow \]\[3\,(x+320)=2400\] |
| \[\Rightarrow \] \[3x+960=2400\]\[\Rightarrow \,\]\[3x=1440\] |
| \[\Rightarrow \] \[x=\frac{1440}{3}=480\,m\] |
| Hence, speed of man \[=\frac{480}{4\times 60}m/s=2\,m/s\] |
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