Discrete Math Computer Science Question

[Noriko Kamachi]

Homework Statement

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

Homework Equations

The Attempt at a Solution

[/B]
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?

 

[Tom.G]

How many bits does the question ask about? Are there any bits it does not ask about?

 

[Noriko Kamachi]

How many bits does the question ask about? Are there any bits it does not ask about?

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.

 

[Tom.G]

Find the probability that a randomly generated bit string of length 10 begins with a 1 or ends with a 00

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