Find the sum to infinity of the geometric series $8 + 4 + 2 + 1 + \ldots$

The first term is $8$ and the common ratio is $\dfrac{1}{2}$, which lies between $-1$ and $1$, so the sum to infinity is $\dfrac{a}{1 - r} = \dfrac{8}{1 - \frac{1}{2}} = 16$. Summing only the four terms shown gives 15.