The fundamentals of punctuality

It’s the first day of school for my kids, so I have a math quiz for you:

In the past, the school the kids attend has started its day at 8 a.m. There were always a certain number of kids who came scrambling in every morning at 8:05. Their parents tended to say things like “We just can’t get there at 8.”

A note: San Francisco doesn’t automatically send kids to neighborhood schools, so most of those who don’t get to school by school bus are driven there by parents or others, even in the upper elementary grades.

This year, the start of the school day has been moved up 10 minutes, to 7:50. Here’s the quiz: If those kids were habitually five minutes late when the day started at 8, how many minutes late will they be now that school starts at 7:50?

Answer: Five.