Answer:
If 400 ml of squash is made by mixing 50 ml of cordial with water, then the remaining volume is water.
The volume of water used in making the squash = 400 ml - 50 ml = 350 ml
The fraction of the drink that is water is:
Water volume / Total volume = 350 ml / 400 ml = 7/8
Therefore, 7/8 of the drink is water.