2.4 cups of orange juice would be needed for 1 cup of pineapple juice. 
Using the parameters given for our Calculation;
- ⅘ cup of oranges = ⅓ cup of pineapples 
We can write a proportional expression as : 
⅘ = ⅓
x = 1 
cross multiply 
x/3 = 4/5 
5x = 3 × 4 
5x = 12 
x = 2.4 
Hence, 2.4 cups of orange juice would be need