# Bit strings

• May 10th 2009, 10:12 AM
creativewisdom
Bit strings
Hello. I am getting confused on the topic of bit strings. Does anybody know how I could go about solving the following problems?

How many bit strings of length 10 have at least eight 1 s in them?

Describe the bit strings that are in the regular set represented by 0*11(0 È 1)*?

Thanks!
• May 10th 2009, 10:59 AM
Plato
Quote:

Originally Posted by creativewisdom
How many bit strings of length 10 have at least eight 1 s in them?

Describe the bit strings that are in the regular set represented by 0*11(0 È 1)*?

Thanks!

There $\binom{10}{8}$ with eight 1's.
There $\binom{10}{9}$ with nine 1's.
There $\binom{10}{10}$ with ten 1's.

I do not understand the notation in the second question.
• May 10th 2009, 11:07 AM
creativewisdom
Quote:

Originally Posted by Plato
There $\binom{10}{8}$ with eight 1's.
There $\binom{10}{9}$ with nine 1's.
There $\binom{10}{10}$ with ten 1's.