a recipe calls for 2 3/4 cups of milk and i want to make it 1 1/2 times smaller. How much milk do I need?
What do you mean by 1 1/2 times smaller?
That's like 150% discount. 100% already takes you down to zero.
Do you mean that 2 3/4 is 1 1/2 times a much as you want? If so, then you want 2/3 as much, or
2 3/4 * 2/3 = 11/4 * 2/3 = 22/12 = 1 5/6