## Elementary Algebra

To convert 500 milliliters to pints, we need to multiply 500 by the ratio that converts milliliters to pints. The ratio that converts liters to pints is $\frac{2.1\ pints}{1\ liter}$. The ratio that converts milliliters to liters is $\frac{0.001\ liter}{1\ milliliter}$. After all, when multiplied by the original expression, these ratios cancel the undesired units and leave us with the desired units, pints. So, the ratio that converts milliliters to pints is $\frac{0.001\ liter}{1\ milliliter}$ $\times$ $\frac{2.1\ pints}{1\ liter}$ = $\frac{0.0021\ pints}{1\ milliliter}$. We then multiply 500 by this ratio: 500 milliliters $\times$ $\frac{0.0021\ pints}{1\ milliliter}$ = 1.05 pints.