# Bit strings

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• May 10th 2009, 11:12 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, 11:59 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.
Add them up.

I do not understand the notation in the second question.
• May 10th 2009, 12:07 PM
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.
Add them up.

I do not understand the notation in the second question.

Thank you so much for your help! You do not understand how much I appreciate that. As for the second question, it comes from my assignment from my online class I am taking in discrete math. I have had issue after issue with rendering notation such as that, which is probably why I didn't understand what it meant. Oh well. Again, I really do thank you for your help.