To find how much the amount of water in the canteen should change every 10 minutes, we need to divide the recommended amount of water by the number of minutes in an hour.
The recommended amount of water is 24 ounces per hour.
There are 60 minutes in an hour, so the recommended amount of water per minute is 24/60 = 0.4 ounces.
Therefore, the amount of water in the canteen should change by 0.4 ounces every 10 minutes.
Answer: 0.4