Computing the Commute

RAY: This was submitted by a fellow named Bob Stewart and I had to change a few things but not much. I liked it just the way it was.

"My friend Jane gets off work at 1:30 every day, well every day that she works, that is. And it takes her one hour to drive home. Since she's not driving at rush hour, she arrives home at almost exactly 2:30 every day - a one hour commute. However, it doesn't always work out that way. For example, one day she left work at the usual time, 1:30 , but got home at 3:30 instead of 2:30 . There was nothing different about her route and she drove the same speed and she didn't break down and she wasn't abducted by aliens or anything like that. So the question is what happened?"

Now I don't want you to infer anything. Just use the information I've given you.

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[ Car Talk Puzzler ]