Solve the following union type question a How many bit str

Solve the following \" union \" type question: (a) How many bit strings of length 8 either begin with 1 0s or end with 1 1s? (inclusive or)

The answer that i keep getting is (2^6) + (2^6) - (2^4)= 112, but WeBWork keeps telling me that it\';s wrong. Can you please explain/answer the question.

-Thanks

Solution

case1:

numbe of bit strings begin with 0s = 2^7

case2:

numbe of bit strings end with 1s = 2^7

case3:

numbe of bit strings end with 1s and begin with 0s = 2^6

So

-----

Answer is = case1+case2-case3

=(2^7)+(2^7)-(2^6)

=192