A train covers half of its journey with a speed of `15 ms^(-1)` and the an other half with a speed of `25 ms^(-1)`. The average speed of the train during the whole journey is

Options

A. `20 ms^(-1)`
B. `175 ms^(-1)`
C. `22 ms^(-1)`
D. `18.75 ms^(-1)`

Answer

D