There are two pints in one quart and four quarts in one gallon. How many pints are there in $2\frac{1}{2}$ gallons of milk?
To find the number of pints in $2\frac{1}{2}$ gallons, I need to multiply the number of gallons by the number of quarts per gallon and then by the number of pints per quart. I can write this as a multiplication of fractions: $2\frac{1}{2} \times 4 \times 2$. To multiply mixed numbers, I can convert them to improper fractions first. $2\frac{1}{2}$ is the same as $\frac{5}{2}$, so I can write $2\frac{1}{2} \times 4 \times 2$ as $\frac{5}{2} \times \frac{4}{1} \times \frac{2}{1}$. Now I can multiply the numerators and the denominators separately: $\frac{5}{2} \times \frac{4}{1} \times \frac{2}{1} = \frac{5 \times 4 \times 2}{2 \times 1 \times 1}$. Simplifying, I get $\frac{40}{2} = 20$. This means there are 20 pints in $2\frac{1}{2}$ gallons of milk. 