# Discrete Math Computer Science Question

1. Apr 8, 2016

### Noriko Kamachi

1. The problem statement, all variables and given/known data
Find the probability that a randomly generated bit string of length 10 begins with a 1 or ends with a 00 if

a)a 0 bit and a 1 bit are equally likely.
b)The probability that a bit is a 1 is .7
c)The probability that the ith bit is a 1 is 1/2i for i=1,2,3,...,10

2. Relevant equations

3. The attempt at a solution

Since I know that the length is 10, and that the first and last two spots are already selected, I only have to worry about the middle 7 spots. A bit can only be 2 choices 0 or 1.

a) If the odds are the same for both, then I just calculated (1/2)7 based on the 7 remaining choices.

b) Probability here would be (.7)7 going by the same remaining choices.

c)For this I did

(1/2)(1+7)*7/2 which would equal a probability of (1/2)28.

Was my approach to this problem correct?

2. Apr 9, 2016

3. Apr 9, 2016

### Noriko Kamachi

A string of length 10 where the choices are either 0 or 1. The first one is labeled as 1, the last two as 00. This leaves seven choices where the selected bit can be 0 or 1.

4. Apr 9, 2016

### Tom.G

What part of this problem statement asks about the seven bits in the middle?