Final answer:
To mix peach squash with water in a 1:2 ratio, for 400 mL of water, you need 200 mL of squash. This is calculated by dividing the water volume by the water part of the ratio.
Step-by-step explanation:
If peach squash is mixed with water in the ratio 1:2 and you use 400 mL of water, then the amount of squash needed is found by setting up a simple proportion. Because the ratio is 1 part squash to 2 parts water, for every unit of squash, you need two units of water.
If the 'unit' is chosen as milliliters, then for every 1 mL of squash, you need 2 mL of water. To find out how much squash is needed for 400 mL of water, we divide the amount of water by the water ratio number: 400 mL of water / 2 = 200 mL of squash. This means you would need 200 mL of peach squash to mix with 400 mL of water to maintain the 1:2 ratio.