This question is really wearing me out, any ideas?

**1. The problem statement, all variables and given/known data**

How many times must I throw a fair dice in order to make the probability of getting at least one ‘6’ greater than 90%?

With this many throws, what is the probability of getting three ‘6’s?

It’s the first part I’m struggling with.

**2. Relevant equations**

The relevant question is the one on the top of the pic attached.

Where

P = probability of outcome interested in

N = number of throws

**3. The attempt at a solution**

Attatched.

I’m using P(1) as the probability of getting 1 six, so n=1.

For the second part of the equation I would use P(3).

http://ift.tt/1qGv7ek