our man Ostap was going hame from kiev. He rod halfway-fifteen times as fast as he goes on foot. The second half he went by ox team. He can walk twice as fast as that. Would he have saved time if he had gone all the way on foot?

Answer 1

He ran halfway, fifteen times faster than walking. So he got there T/30 where T is the total walking time.
The second half, he walked, and it took 2*T/2 or T minues.

Total time: T+ T/30
Well, if he had walked it would have taken him only time T.

Answer 2

Yes.

Compare the time D/V to the time
(D/2)/2V + (D/2)/(V/2)= D/4V + D/V