Tuesday, November 22, 2016

More Faculty Lounge Math

     My teaching life pre-MTBoS was certainly different than it is now.  I look at student work differentlyplan lessons and activities differentlyprovide feedback differently, even think of myself as a math learner in a different way than I did before becoming an active part of this amazing community.  But nothing has changed more than the way I look at what I see around me.  My friend Graham Fletcher has taught me that what I'm doing is called mathematizing the world, and now that I've started, I can't seem to stop.  In that spirit, here's another edition of Faculty Lounge Math.

     This is more like a 2-Act than a 3-Act...

What fraction of the container is filled with pretzels?

Does this help?

  This one got tweeted out:

Rainbow Cookie

Fractions anyone?

A Faculty Lounge 3-Act

Act 1

Washing Up from Joe Schwartz on Vimeo.

Main Question: How many squirts will the machine dispense until it runs out of soap?

Act 2

Inside.  According to the company, 0.4 mL of liquid foam soap is dispensed each time it's activated.

The dispenser holds 1 bag.  Each bag holds 1,200 mL of foam soap.  
Act 3

  My first attempt at figuring this out didn't go so good.

I added 3 + 10 + 100.  I don't know... 113 handwashings just seemed too low.

So I tried something different...

3,000 was more like it!

Where did I go wrong?

Thinking additively, not multiplicatively.

 Act 4: The Sequel
The dispenser can be set to squirt 0.7 mL of soap per activation.  How many hand washings per bag?

   A jar of pretzels, trays of muffins, a cookie, a soap dispenser; in my previous life they would have been things to eat and a way to promote good hygiene.  But thanks to DanAndrewGrahamMarilynRobertTraceyMichaelSimonKristinFawnMax,  Annie, Andy, and the rest of the MTBoS crew, I now see them as opportunities to notice and wonder, estimate, spark a number talk, and create and solve problems.  It's a gift I'm thankful for.  Hope they don't mind if I re-gift.


  1. Please keep regifting!!!
    You've all had an impact on me as well. I respond to my students' math writing differently because of your influence.

  2. Great problem for 5th graders to figure out!!

    1. Thanks Josh. I'm anxious to try it out with our fifth graders and see what they come up with!

  3. I love this hand soap problem. I am working with a teacher and we are about to start exploring mult. and dividing w/decimals with her 5th grade students. I think we will try this. I wonder if we could test whether or not the math matches the situation. Maybe we could put a piece of paper next to the soap and everyone could make a tally when they used the soap??

    1. Thanks Sarah. I've thought of something similar: put a piece of paper by the dispenser one morning and have everyone that uses it make a tally. Then we'd know about how many uses it gets per day. Then the kids could figure out how many days one full bag of liquid soap would last. I'm also thinking about representing the 0.4 as 4/10 since we're working right now with fractions. Lots of math there, and I'm not even talking about the paper towels they used to dry their hands!

  4. Keep up the great work and inspiration, Joe!

    1. Thanks Andrew! I appreciate your ongoing encouragement and support.