Welcome to Gaia! ::

Okay,
so there are ten people on a boat out at sea, when pirates come along and take them captive.

Now the pirates aren't your ordinary pirates who just kill everyone, they like to give everyone a chance to live.
So they line everyone up in such a way that each captive can only see the captive in front of them.
The pirates than place either a black or a white hat on each captives head. They have no idea what the colour of the hat on their head is.
Then, starting from the captive at the back of the line, they ask each captive to guess the colour of their hat. If they guess right they are allowed to live, if they get it wrong they have to walk the plank.

The question is what can the captives do to guarantee that at least 9 out of ten of them would survive?

The number of hats of each colour is irrelevant to solving the riddle

This is a bogus "riddle." The answer revolves around the prisoners agreeing to a way of communicating information through their responses. The "correct" answer is something to the effect of giving a positive answer (my hat is white) if the next person's hat is white, while giving a negative answer (my hat is not black) if the next person's hat is black.

The first problem is not an actual riddle, but rather a puzzle. The second problem is the "correct" answer is no more valid than having each person say, "The person in front of me is wearing a black hat and i am wearing a white hat." Without listing what constraints exist upon what answers are allowed, it becomes silly.

Another possibility would just be to cough if the next hat is black. Or you could insert the phrase, "I think" to convey the information, or... Yeah. It is just a bad puzzle.