Physics brain teaser---really hard (now that i got your attention, please look at the question)?

Question

Fake Coin
Imagine that you have in front of you fifty coins. They all look exactly alike except one of them is a fake. Because it's a fake, it weighs a couple of grams more than a real coin. So, if you had a balance scale, and you knew which one was the bogus coin, you would put it on one side of the scale, and a good coin on the other side. It would be immediately obvious from this imbalance which one was the phony coin, because it's heavier than a real coin. Knowing that, you have in front of you fifty coins -- one of which is bogus and a balance scale. The question is: how can you determine which one is the fake in four attempts?

Answer 1

24 - 24, 8 - 8, 3 - 3, 1 - 1 = answer.