## Precalculus (6th Edition) Blitzer

The probability of getting a tail in all the seven tosses is $\frac{1}{128}$.
We know that the probability of getting a tail in a single toss of the coin is as follows: Number of favorable out comes $n\left( e \right)=1$ (tail) Number of total out comes $n\left( s \right)=2$ (head and tail) $P\left( \text{tails} \right)=\frac{1}{2}$ And the probability of getting a tail in all the seven tosses is given below, \begin{align} & P\left( \text{seven tails} \right)=\frac{1}{2}\times \frac{1}{2}\times \frac{1}{2}\times \frac{1}{2}\times \frac{1}{2}\times \frac{1}{2}\times \frac{1}{2} \\ & =\frac{1}{128} \end{align} Thus, the probability that a tail will come in all the seven tosses is $\frac{1}{128}$.