# To Accumulate a Rate — Integrate!

Teaching High School Mathematics

# Rumor has it…

I taught a lesson today on Euler’s Method using a differential equation that models the rate that a rumor is spread. The lesson went great, but the real kicker was the setup. I utilized my problem solving class the day before to start a rumor for me that I had lost a bet and got a tattoo of a Pi symbol on my arm. (Not a bad idea by the way.) They got on Twitter and started the rumor for me.  I have three Calculus classes 1st, 2nd, and 3rd periods. By the next morning students were quite anxious to ask if I had a tattoo and I didn’t give them a straight answer.

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I started out saying that today we are going to talk about rumors. I talked about how rumors spread and how it feels to have a rumor spread about you. Over half of each class had heard the rumor about my tattoo. I told them there was actually an equation that you could use to model how a rumor spreads. Most students were still wondering if we were doing math today or if I was just complaining about people spreading rumors about me. We did Euler’s method with half day step size and found that with the growth constant I chose that almost all of the school would have heard the rumor in 5 days. They were still pestering me to reveal a tattoo which I had anticipated, and I was ready. I told them that If everyone had the assignment correct the next day then I would roll up my sleeve. I needed to clarify that it was on my arm, because some of the rumors had already morphed into a Pi symbol on my butt or a tramp stamp. I wanted to squelch that idea, but it did allow me to talk about the constant in the equation and how the “juiciness” of the rumor might effect the equation and growth rate.

That night I got a gel pen and made a tattoo to keep the fun going. I printed out a Pi symbol and flipped the paper over and filled it in with gel pen ink. I slid some deodorant on the back of my shoulder and then put the paper on my back with a wet rag like a fake transfer on tattoo. My son had to fill it in. Here is the pic I got.

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The next day In class there were a couple of students who messed something up and so I told them I would show them a picture instead.

My Euler’s method lesson has never been so exciting. I have a whole year to think up a new rumor to spread for next year’s lesson.

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### 5 comments on “Rumor has it…”

1. Sara Dalton
March 15, 2015

I loved reading about your lesson on Euler’s Method. The set up was amazing! And what a great way to “integrate” Pi into your current topic of study on the day before March 14th. I love reading about great anchor tasks–tasks that are so mathematically rich and intriguing to students that the lesson is “taught” by students engaged in mathematical exploration.

• kaleb40
March 15, 2015

Thanks! I had such a fun time with it!

2. Tina C.
January 25, 2016

Hello! This post was recommended for MTBoS 2015: a collection of people’s favorite blog posts of the year. We would like to publish an edited volume of the posts and use the money raised toward a scholarship for TMC. Please let us know by responding via email to tina.cardone1@gmail.com whether or not you grant us permission to include your post. Thank you, Tina and Lani.

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