Sunday, October 13, 2013

MTBoS - Backyard Ice Rink

Each year my husband constructs one of our family's favorite after school spots ... our backyard ice rink.  (It's a Minnesota thing.)  Anyways, each year I pose a very important question to my students,

"How long will it take to flood the rink?"  

First, I have them write down an estimated time in hours.  We talk about how they came up with their estimate and if they need any additional information.  They get out their paper and pencil and start brainstorming questions for me.
  • What are the dimensions of the rink?  
    • 36 x 64 feet
  • How thick should the ice be?
    • at least 4 inches thick
  • What long is the garden hose?
    • 50 feet
  • What is the circumference of the garden hose?
    • 3/4 inch
  • How many gallons come out of the hose each minute?
    • We look it up together here
  • How many gallons are in a cubic foot?
    • We read about it here
This is one of my favorite lessons of the year.  This problem is so rich with math.  Do we ever get the exact answer?  No.  I have done this problem for 3 years with a dozen different Geometry classes and each class obtains a slightly different estimate.  I let my students lead because they ask the BEST questions.  They debate about factors such as weather and time of day.  Some classes add or subtract hours due to weather just as some classes add or subtract hours due to the time of day.  (FYI - We do not get into water pressure and what kind of well we have at my house.  Maybe this year I will check into it.)

It's pretty incredible.  Try it.  See what you come up with!

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