You know those tests where you get a series of numbers and have to find out the underlying rule.
Here's one for traders: the rate of a certain currency follows a simple rule, without any random deviation. The rates of the last 12 days:
3, 6, 6, 8, 8, 7, 7, 9, 8, 8, 6, 9
If you can figure the rule, you know when to buy or sell and you'll get obscenely rich. What's the rates of the next 3 days?