Math Help - Please help me with this probabilty question

1. Please help me with this probabilty question

A Blum-Blum-Shub random number generator produces a string of random bits. A bit is random if the probability of it being 0 or 1 is 1/2 . Let’s assume a random bit number is generated.
a.What is the probability that a string with all 1’s is generated.
b. What is the probability that a string with k 1’s is generated.

2. Originally Posted by aravindchow3
A Blum-Blum-Shub random number generator produces a string of random bits. A bit is random if the probability of it being 0 or 1 is 1/2 . Let’s assume a random bit number is generated.
a.What is the probability that a string with all 1’s is generated.
b. What is the probability that a string with k 1’s is generated.
How long is the string meant to be?