Answer:
To solve the problem, we can use the following formula:
Final amount = Initial amount x (1 - rate)^(time)
where the rate is expressed as a decimal and time is in the same units as the rate.
In this case, the initial amount is 100% (since it's a full tank), the rate is 4% per minute, and the time is 20 minutes. Substituting these values into the formula, we get:
Final amount = 100% x (1 - 0.04)^(20) = 41.97%
Therefore, after 20 minutes of leaking, there would be approximately 41.97% of the water left in the tank.