Answer: 260 gallons
Step-by-step explanation:
We can use a proportion to solve this problem. We know that a family used 15 gallons of milk every 3 weeks. Since the problem asks for how much they will need for a year, we can gather that a year is 52 weeks. We can come up with the following proportion.
[tex]\frac{15}{3} =\frac{x}{52}[/tex] [cross multiply]
[tex]3x=780[/tex] [divide both sides by 3]
[tex]x=260[/tex]
Therefore, they will need to purchare 260 gallons.
