PROBLEM:

Approximately how many atoms thick is a cell membrane, assuming all atoms there average about twice the size of a hydrogen atom?

SOLUTION:

The cell membrane is 10^-8 m while the hydrogen atom is 10^-10  m. The number of atoms in the cell membrane is

\begin{align*}
\text{no. of atoms} & =\frac{\text{d}_{\text{m}}}{2\text{d}_{\text{H}}}\\ \\
& =\frac{10^{-8}}{2\left(10^{-10}\right)} \\ \\
& =50\:\text{atoms} \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)
\end{align*}