you have got an error in the sentence:
"This means that the probability of getting 101 is $1/2 \times 1/2 \times 1/2 \times 1/2 \times 1/2 = 1/2^5.$"
The right sentence is :
This means that the probability of getting 101 is $1/2 \times 1/2 \times 1/2 = 1/2^3