Using only the digits 0 an 1, how many different numbers consisting of 8 digits can be formed?

Answer 1

Can your leading digit be 0 ?

if so, then the number of cases = 2^8 = 256
if not, the the number of cases = 1*2^7 = 128

(looks like you are studying the binary number system)

Answer 2

yeah its the first one. thank you!