*pushes thick glasses up nose* Actually, it would takes about 300 piranhas 5 minutes to eat a full grown human. If you take the fact that a small child is roughly a fifth the side of a grown human, then it would take roughly 60 piranhas 5 minutes to eat a small child. Now for in order for 1 piranha to eat a small child, we have to use this conversion. 5 minutes = 300 seconds. In this case it would take 18000 seconds for the 60 piranhas to eat a small child. Now if you take this number times 60, you would get the number of seconds it takes one piranha to eat a small child. 1,080,000 seconds. Convert that to days and you would get 12.5 days. By this time the child is dead from either starvation, dehydration, or drowning. Considering piranhas are freshwater fish, the child wouldn’t die of thirst. But given the fact that piranhas are native to the Amazon river, and the fact that the Amazon has millions of harmful bacteria, the child would die from some form of poisoning. The more realistic death of this child would be the fact that either a) they can’t swim or b) they run out of energy. Verdict: child would drown before they got eaten.