Eight antique coins,one of which are fake and weights less.

Question

How can you find the fake coin in: 

1. Three weighings

2. Two weighings

Answer 1

2. In two weightings.

Put 3 and 3 coins on the scale.

If equal, remove them and put the rest 2 coins to find the fake

If not equal, then from the group of three coins which are lighter, take any two and put on scale. If one of them is fake, the scale will imbalance identifying the fake coin: if equal then the third coin (not on scale) is fake