A) 36 km/h
B) 48 km/h
C) 54 km/h
D) 60 km/h
Correct Answer: C
Solution :
[c] Speed of the first train\[=\left( \frac{100}{10} \right)\,m/s=10\,m/s\] Let the speed of the second train be x m/s. Relative speed\[=(10+x)\,m/s.\] \[\frac{200}{(10+x)}=8\] \[\Rightarrow \] \[8\,(10+x)=200\] \[\Rightarrow \] \[8x=120\] \[\Rightarrow \] \[x=15\] Speed of the second train \[=15\,m/s\] \[=\left( 15\times \frac{18}{5} \right)\,km/h=54\,km/h.\] |
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