graphite is made up of layers of graphene. each layer of graphene is about 200 picometers, or 200×10⁻¹²…

Explanation:

Step1: Convert 1.6 mm to meters

Since 1 mm = $10^{-3}$ m, then 1.6 mm = $1.6\times10^{-3}$ m.

Step2: Calculate the number of layers

Let $n$ be the number of layers. We know that the thickness of one - layer is $t = 200\times10^{-12}$ m and the total thickness is $T=1.6\times10^{-3}$ m. Using the formula $n=\frac{T}{t}$, we substitute the values: $n=\frac{1.6\times10^{-3}}{200\times10^{-12}}$. We can rewrite this as $n=\frac{1.6\times10^{-3}}{2\times10^{2}\times10^{-12}}$. Using the rule of exponents $a^{m}\times a^{n}=a^{m + n}$ and $\frac{a^{m}}{a^{n}}=a^{m - n}$, we have $n=\frac{1.6}{2}\times10^{-3-( - 12 - 2)}$. $n = 0.8\times10^{11}$. In scientific notation, we rewrite it as $n = 8\times10^{10}$.

Answer:

$8\times10^{10}$