Answer:To determine the amount of water needed to fill the whole tank, we first need to find the capacity of the tank.
Given that Timothy pours 20 quarts of water into the tank and it is 1/5 full, we can set up a proportion to find the total capacity.
1/5 represents the portion of the tank that is filled, so we can write the proportion:
(20 quarts) / (1/5) = x / 1
To simplify the proportion, we invert the denominator and multiply:
(20 quarts) * (5/1) = x
100 quarts = x
Now we know that the capacity of the tank is 100 quarts. To convert quarts to gallons, we divide by 4 since there are 4 quarts in a gallon:
100 quarts / 4 = 25 gallons
Therefore, Timothy needs 25 gallons of water to fill the whole tank.