Depends where you hit them, and what type or age or elephant it is. Concentrating the fire on the head could work, but if the arrows are shot from far off it is possible they will just 'rebound' off the skull. Shooting them in the side might work if you have shitloads of arrows and can hit hard and lucky enough to penetrate a major organ.
Anywhere from 10 to a few hundred, depending on your luck and skill.



