Final answer:
The tap was open for approximately 15 minutes.
Step-by-step explanation:
To find the number of minutes the tap was open, we need to divide the total amount of water that came out of the tap by the rate at which water comes out.
Given that 2.5 liters of water come out of the tap every minute and 38.5 liters of water came out, we can use the equation:
Number of minutes = Total amount of water / Rate of water flow
Substituting the given values, we get:
Number of minutes = 38.5 liters / 2.5 liters per minute
Number of minutes = 15.4 minutes
Therefore, the tap was open for approximately 15 minutes.