To find the ratio of concentrate to water, we need to first determine how much water is used in each bottle.
Given that each bottle is filled with 300 mL of liquid and 50 mL of concentrate, the amount of water used is:
Water = Total volume - Concentrate volume
= 300 mL - 50 mL
= 250 mL
Now, to find the ratio of concentrate to water, we divide the volume of concentrate by the volume of water:
Ratio = Concentrate volume / Water volume
= 50 mL / 250 mL
= 1/5
So, the ratio of concentrate to water used is 1:5 or 1/5 in fraction form.