Answer:
They need to buy 3 litters of lemonade, 1.5 litters of pineaple juice and 1.5 litters of ginger ale.
Explanation:
In order to calculate the amount of each ingredient they need for 6 liters of punch we can first create fractions for each ingredient based on the proportions we were given. This is shown bellow:
2 litters lemonade + 1 litter pineapple juice + 1 litter ginger ale = 4 litters punch
Then we have:
lemonade = 2/4
pineaple juice = 1/4
ginger ale = 1/4
If we want to make 6 liters of punch we can just apply this fractions to know how much of each we need:
lemonade = 6*(2/4) = 12/4 = 3 litters
pineaple juice = 6*(1/4) = 1.5 litters
ginger ale = 6*(1/4) = 1.5 litters
They need to buy 3 litters of lemonade, 1.5 litters of pineaple juice and 1.5 litters of ginger ale.