"It's one mile closer to us than it is to Portland," Samuel said. We turned to stare at him.
"And how do you figure that?" we asked.
"Well, the first exit to Olympia is 109, the next one is 107. We are at Exit 212. So Exit 107 is one mile before the halfway point from our exit to the Washington/Oregon border." (It's been years since he's been to Olympia. How did he remember the exit number??)
That settled it. Now we know, once you get to Olympia, you have that distance again plus one more mile till you get to Portland.