Answer:
50 Minutes
Explanation:
For the empty tank to hold the same amount of water, we can simply take the total water of the full tank divided by the rate, divided by two to allow both tanks to be equal, aka, half.
500 L / 5 L per minute / 2
100 minutes / 2
50 minutes.
For both tanks to have the same amount of water, 250L, it would take 50 minutes with a flow rate of 5L per minutes.
Cheers.