Another probability question

Say you have a coin weighted to show heads 60% of the time. How many coin tosses are needed to have 90% confidence of getting more heads than tails?

toss the coin until you have more heads than tails.

then you can be 100% confident that you have more heads than tails.

The market is very slow today and coin tossing seems to be all the rage. I am curious, though. Why go to all that trouble only to make the coin weighted for 60% heads ? If you are going to tamper with it, isn't it better to make both sides of the coin heads ? Then you are 100% certain of a win, 100% of the time.

Also is there something special about 60% that people keep mentioning it. I am puzzled as I prefer 100%.

I prefer a coin with 30% heads that pays 10 heads and losses 1 for tails.

Expected win: 0.3 x 10 - 0.7 x 1 = 2.3

What about that?

I agree, nothing special with 60%. It is just a bug in their head. They need some reprogramming.

That's all well and good Albert - top marks for understanding expectancy. But can you solve the probability question?

2.512941595

I feel some uncertainty Mr Bramble...

That's definitely a good thing.