The Math of a Leaking Swimming Pool

Our pool at Arapahoe leaks 1 inch in 12 hours.  Local people are outraged by the amount of water used.  Give an argument of why they should or should not be outraged.

Water is a hot topic here in southwest Nebraska.  Farmers are limited on the amount that they can use on their fields, and the cost of it can no longer be ignored for us city dwellers.  It has been told that the local swimming pool leaks 1 inch of water in a 12 hour period.  A community member asked me if this was a significant amount of water and wondered if anything should be done.  I split my students into groups, gave them all tape measures, and asked them the same question.  This time of year the pool is empty, so students can wander in and out of the pool and measure any portion of it they wanted.  I gave them no directions, but made it a competition.  The group with the closest answer and the best explanation would win their name on my wall.

I loaded up a bus full of kids (Having a bus permit has its advantages) and we ran down to the pool.  I gave them the entire period to take as many measurements as they wanted.  I also wanted the capacity of the pool while we were there.   The next day I graded tests and acted uninterested as they worked on the mathematics.  I had four groups and just listened from my desk to all discussions taking place.  The discussions were incredible.  They had several arguments break out.  The bottom of the pool was the most perplexing.  Groups were not sure how to handle the sloped bottom.  Two of the groups decided on the average depth.

After their calculations were completed, we found that the pool leaks about 16 acre-inces a year.  This is not very much water in the grand scheme of things.  The cost of pumping this much water would be small.

Next year I will probably develop this problem farther.  It was a good problem.  I am also thinking that all my teacher prep courses that told me not to use competition in the classroom were full of *&^%.  Competition seemed to make this group come alive.

2 thoughts on “The Math of a Leaking Swimming Pool

  1. Hi Dan, A couple of observations. First of all, your low key approach to kids and problem solving is the best! I have this image of you driving the bus and taking in all of the conversation. Your problems are so real! Love it! Linda Hayek

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