# How do you calculate the mass of 3.24x10^18 atoms of iron?

It is a fact that $\text{Avogadro's number}$ of iron atoms have a mass of $55.85 \cdot g$.
Since $\text{Avogadro's number}$ $=$ $6.022 \times {10}^{23}$, mass of iron, $=$ $55.85 \cdot g \times \frac{3.24 \times {10}^{18}}{6.022 \times {10}^{23}}$ $=$ $3 \times {10}^{-} 4 \cdot g$.