This question is a little confusing as im not sure if you mean at the same time or individually but i will answer to the best of my ability. I've taken taw-kwon-do for almost 9 years and have achieved the rank of sr. 1st degree blk belt. In advanced classes we are taught how to defend against multiple attackers but you shouldn't rely on strictly karate or tae-kwon-do to accomplish this. duration depends on your skill level so i can't give you a definite answer.
