Answer: The required number of gallons to travel 550 miles is 25.
Step-by-step explanation: Given that a van travels 220 miles on 10 gallons of gas.
We are to find the number of gallons that the van needs to travel 550 miles.
We will be using the UNITARY method to solve the given problem.
We have
Number of gallons required to travel 220 miles = 10.
So, number of gallons required to travel 1 mile

Therefore, the number of gallons required to travel 550 gallons will be

Thus, the required number of gallons to travel 550 miles is 25.