A) 60 km/hr
B) 58 km/hr
C) 54 km/hr
D) 64.8km/hr
Correct Answer: C
Solution :
Distance travelled by X in 4 hrs 48 min after they meet \[=45\,x\left( 4+\frac{48}{60} \right)\Rightarrow 45\,x\frac{24}{5}=216\,km\] Speed of train Y= x km/hr \[\Rightarrow \]Distance AM = x \[\times \] (3 hrs + 20 min) = \[x\times \frac{10}{3}\Rightarrow \frac{10x}{3}km\] Now, Time taken to reach A by Y = Time taken to reach A by X \[\Rightarrow \frac{216}{x}\frac{\frac{10x}{3}}{45}\Rightarrow \] Shortcut method: - Speed of 2rd train (Y) = speed of 1st train (\[\times \]) \[\sqrt{Ratio\,\,of\,\,their\,time\,\,after\,\,they\,\,met.}\] \[=45\times \sqrt{\frac{\frac{24}{5}}{\frac{10}{3}}}=45\times \sqrt{\frac{24\times 3}{50}}\] \[=45\times \frac{6}{5}=\]You need to login to perform this action.
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