we know that the ratio is 1:3 that means (1+3)=4 liters To prepare 4 liters of fruit punch use 1 liter of orange juice and 3 liters of pineapple so to Make 3 Liters of fruit punch the proportion to find the pineapple liters will be 3/4=x/3------> x=9/4-----> 2.25 liters of pineapple
