To find out the proportion of the total storage capacity that each truck received, we need to follow these steps:
1. Determine how much of the tank is left after 5 trucks are filled: Since three-fourths of the tank is emptied to fill the 5 trucks, one-fourth of the tank is left (1 - 3/4 = 1/4).
2. Calculate the proportion of the total capacity that each truck received: Since there are 5 trucks and one-fourth of the tank's capacity is left for them, each truck received 1/5 of 1/4, which simplifies to 1/20 of the total tank capacity.
Therefore, each truck received 1/20 of the total storage capacity of the tank.