*Originally posted by royalchicken*

**129 coins lie on a table. Of these coins, 128 are fair and the other has heads on both sides. After picking a coin at random, ignorant of its nature, you flip it eight times, turning up eight consecutive heads. What is the probability that the ninth is a head?**

I'm not great at statistics but:

You have a 128/129 chance of getting a fair coin.

A fair coin would give you 1/2 of getting a head.

It doesn't matter that you got 8 heads already it's still 1/2.

So, 128/129 x 1/2 = 128/258 chance of it being a head?

But you have 1/129 of getting the bent coin.

This would give you a probability of 1 of a head.

1/129 x 1 = 1/129.

So the answer is 128/258 because this is more likely than picking the bad coin?

I told you I was no good at probability ðŸ˜³