Question

how many bit strings of length 9 have exactly two 1'S or two 0'S( this is one question, so you should have one answer)

Answer 1

Answer:

72.

Step-by-step explanation:

Number of strings with exactly 2 1's

= 9C2

= 9*8/2*1

= 36.

Same for  2 0s

= 36.