Well, we know that 3:1 is one batch of orange water. We also know that there are 2 things to focus on.
1. Must write ratio for 2 batches of the recipe.
2. Must write ratio for 4 batches of the recipe.
To make this equation simple, double the ratio to find 2 batches because all it means is 2x more water.
3:1
x2
6:2
So, the ratio would be 6:2 to make 2 batches.
To make it easier again, we just multiply the ratio of 2 batches by 2 which would find the ratio for 4 batches.
6:2
x2
12:4
So that means, that it is 6:2 for 2 batches, and 12:4 for four batches.