MTBos Mission #1: 3-Act Hanging by a Hair

I have been a huge fan of Dan Meyer and his 3-Act approach to problem solving Unfortunately, almost every 3-Act task I have come across on his website and over the web involves middle school standards concepts and beyond. No problem though, because as educators WE CREATE!  This is probably one of my most favorite/rich tasks I have created in the past 2 years because it gets students engaged and they don’t care that they’re doing math (and lots of it)! I have seen Dan speak 3 times in the past month (almost reached stalker status) and he said I need to start sharing my elementary 3-Act tasks and so….I guess there’s no better place to begin than here!  Thanks for the push Dan!

Act 1: Watch the video (what questions do you have, what are you curious about, or what do you want to know?)

Usually students will ask how much does he weigh? or how many pieces of hair does he have? which leads me to ask the question, if students haven’t done so, How many pieces of hair would you need to support your body weight?  Students make an estimate which is revisited throughout the lesson.  I try to never underestimate the power of estimation because of the insight it gives me into my students reasoning.  In groups, students test the tinsel strength of a single strand of hair by taping pennies to it until it snaps.  Before reading on…how many pennies can a single strand of hair support? Get it? Got it? Good!

After students have determined the tinsel strength of their hair they can adjust their estimate if they choose to and figure out how many pieces of hair they need.

Act 2: Almost immediately, students realize that they do not have enough information to solve the problem and create a wish list of information they need.  They only get the information if they ask for it and explain what they’ll do with it.  I tell them that information can be dangerous if they don’t know what to do with it!

a penny weighs 2.5 grams or 0.08 ounces

16 ounces in a pound or approximately 456 grams in a pound

Testing the tinsel strength of hair.

Tinsel strength

Act 3: Students are pretty good to go from here however they are still expected to compare and share solution strategies and check they reasonableness of their estimate. BTW-a single strand of a students hair will usually support about 25 pennies.  How close was your estimate?

Act 4: (The Sequel)  I love this part because having students make generalizations and “algebrafy” the math is something I am always trying to improve as an elementary teacher.  In Act 4 I ask students to find the rule that would determine how many hairs would be needed for a person of any weight?  And…can they write it as an expression?

I am always sure to share the disclaimer with my students that they should not use their new-found knowledge on their brother or sister.  Trust me…some have asked!  Although I created the task for elementary students it has really engaged middle school students and teachers during PL sessions.  If you choose to do the task I’d love to hear about it!  The lesson plan is already to go

If you can make it better or have suggestion I’d love to hear from you!

About gfletchy

K-8 math consumer trying to listen and learn each day. Stay thirsty my friends!
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4 Responses to MTBos Mission #1: 3-Act Hanging by a Hair

  1. Kristin says:

    So cute! 3-Act for elementary kids. Love it! I use Dan Meyer’s tasks, too, but I teach middle school, so it is more convenient. I was lucky to take a class at Stanford 2 summers ago, that he helped teach. So fun!

  2. This is awesome!! I love the strange intro that gets them interested and the connection to creating an equation. One of my good friends is an elementary teacher and I tell her about 3-acts and other things from the MTBoS and she is finding it hard to adapt. I can’t wait to share this with her!

    • gfletchy says:

      Thanks Jessica and please do share away!! I have shared this task with lots of colleagues and it is awesome to hear back from them how it takes on a life of its own.
      If you know anyone else or a blog that creates 3-acts for elementary grades please let me know. I’ll be posting one that I created for my wife’s kindergarten class in the upcoming weeks… in addition to more. At first I thought 3-Acts in Kindergarten?!?! And then I replied “why not kindergarten?”
      I guess it’s all about a Growth Mindset!

  3. TiffanyDawn says:

    Thank you for sharing! My kiddos will love this task. They are always interested in weird little facts like this and I am glad that you chose something so out of the ordinary!

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