Why Ke mana and not Di mana ?
I had the same question. "tujuan" is a goal, which is defined as the end toward which effort is directed. This "direction" is the reason why "ke" is preferred.
Why not "Di mana tujuan DIA"
Badly translated into English, Ke would be 'to where is his goal' and di would be 'at where is his goal'. So ke makes the movement and traveling of going to a destination more obvious.
So either translation would be right
dia tujuan di mana
This doesn't make sense. Di mana tujuannya should be correct.
Exactly what I said, Bij4
Either is right depending on context, yes?