# What is the mass if the density = 6.0 g/mL and the volume = 18 mL?

Jan 30, 2016

The equation for density is $\rho = \frac{m}{V}$
Where $\rho$=density, $m = m a s s$ and $V$=volume

#### Explanation:

Fill in what you know:
$\frac{6.0 g}{m L} = \frac{\text{mass } g}{18 m L}$

Multiply both sides by $18 m L$ to get rid of the fraction:
$\frac{6.0 g}{m L} \cdot 18 m L = \frac{\text{mass } g}{18 m L} \cdot 18 m L$

$\frac{6.0 g}{\cancel{m L}} \cdot 18 \cancel{m L} = \frac{\text{mass } g}{\cancel{18 m L}} \cdot \cancel{18 m L}$

$\to \text{mass } = \left(6.0 \cdot 18\right) g = 108 g$

Of course you could have done this faster by first reworking the equation into:
$m = \rho \cdot V$ but that is not evident to everybody.