question_answer

A train runs x km at an average speed of \[{{K}_{1}}\]km/h and y km at an average speed of\[{{K}_{2}}\]km/h. The average speed of the train for the entire journey is:

A)  \[\frac{x+y}{{{k}_{1}}+{{k}_{2}}}\,\,km/h\]  

B)  \[\frac{{{k}_{1}}{{k}_{2}}(x+y)}{x\,{{k}_{2}}+y\,{{k}_{1}}}km/h\]

C)  \[\frac{x\,{{k}_{1}}+y{{k}_{2}}}{{{k}_{2}}+{{k}_{1}}}km/h\]         

D)  \[\frac{xy\,\,({{k}_{1}}+{{k}_{2}})}{x{{k}_{1}}+x{{k}_{2}}}km/h\]

E)  None of these