Bedtime Math

You’ve probably heard of Read 20, a movement where parents are encouraged to read with their children at least 20 minutes a day. But Bon Crowder thinks that this shortchanges math, so she started an initiative that she calls Count 10, Read 10. While I dislike the name — math is so much more than counting — I love the sentiment.

My sons are regularly exposed to more than 10 minutes of math during daylight hours, but I’m still happy to give them another 10 minutes of math right before bed. Sometimes we use the material from Bedtime Math, but I hate the traditional problems that they serve up. I prefer instead to create new, original problems that are a bit more interesting.

This is a double-edged sword.

My kids love the problems I create, but now they’ve come to expect a new problem daily. So every night while they’re brushing their teeth, I’m mentally preparing a bedtime math lesson plan.

This has caused a lot of angst. I’m just not that creative. But two evenings ago, I crafted a problem worth sharing.

Like most five-year-olds, my kids are infatuated with the seasons. They know that the vernal equinox is usually on March 21 (they forgot, and so did I, that it’s on March 20 in 2013), they know that there is an equal amount of daylight and darkness on the equinox, and they also know that the days will continue to get longer until the summer solstice. [update – Thanks to Caitlin for the reminder about the equinox in 2013.] I asked a few questions about these facts to prime the pump, then I posed this question:

What is the difference between the number of minutes of daylight and the number of minutes of darkness today?

Alex speculated that there are two minutes more of daylight every day, so he guessed that there would be 14 more minutes of daylight. Eli made a wild-ass guess and thought it would be closer to an hour.

This led to a great discussion. If there are 12 hours of daylight on March 21 and there are approximately 15 hours of daylight on June 21 (in northern Virginia, anyway), and assuming a linear increase, then approximately 3 hours ÷ 90 days = 2 minutes of daylight are added each day. So the estimate of 14 minutes was actually pretty accurate.

As it turns out, the vernal equinox doesn’t really have an equal number of hours of daylight and darkness. There were exactly 12 hours of daylight on March 17, and there were 12 hours, 10 minutes of daylight on March 21. On March 28, there were 12 hours, 28 minutes, so the difference between that day and March 21 was actually 18 minutes.

But who cares?

The math discussion we had as a result of this question lasted at least ten minutes, so we met the goals of Count 10, Read 10. But as I said above, my kids get way more than ten minutes of math a day. Earlier today, they amused themselves for half an hour with the following problem:

Start at the 1 in the lower left corner. With each move, proceed up or to the right (never left or down). As you move, perform the operations. What path will give the maximum value when you reach the 1 in the upper right corner?

Hopefully, you’ll be able to solve this problem in less than 10 minutes before you go to bed tonight. Good luck!