My Mother, The Genius

Recently, I was out of town with my mom and stepdad and we had to find our way to a restaurant in our rental car. I was driving and my mom was navigating from the passenger seat, her Google Maps directions in hand. Here was the exchange as we drove down the interstate through downtown Omaha:

"We're taking Exit 262. Look for 262," she said.
"Okay," I replied.
"There's Exit 256 - we're looking for Exit 262."
"I know."

A few minutes later, she chimed in again. "Here's Exit 258. We're getting off at Exit 262," she said once again.
"I know, you already told me that several times. We'll be there in four miles."
"How do you know that?"

I looked at my mother with what was surely a puzzling expression. "Because 262 minus 258 equals 4. The Exit numbers correspond with mile markers. You do know that, don't you?"
"They do?," she asked.
"Mom, you're 60 years old. Have you really gone your entire life not knowing this?"
She chuckled with that familiar, knowing laughter that says "you three boys have turned my brain into mush - it's your fault." I guess she has a point. But I still shake my head when I think about all those years of car trips when we were little - before GPS and computer map applications, when all we had was a trusty old road atlas. It's a small wonder that we ever made it to any those destinations.