Class Opener – Day 49 – A Magical Prime?

Today is student choice day, where I look through the Edmodo submissions from my students and choose a short and snappy opener.  Chris B. submits this number “magic” as a video worth sharing with the class:

What’s going on here? Is it just plain coincidence? Dumb luck? The devil’s work? 37 is certainly not a number we encounter too often in our daily math life.

A student in my afternoon class quickly picked up on the mystery:

37 times 3 is 111, and they all have 111 in them

Good enough. Converting a division example from the video into multiplication helps verify the claim”

777 = 37 * 21
111 * 7 = 37 * 3 * 7

It’s a quiz day, but I leave the class with the following challenge:

Develop a similar pattern for a longer string of identical numbers

They are pretty easy to find, such as the one below for five-digit strings. And Chris provided a low-stress math challenge to get us into math thinking mode before our quiz.

numbers

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s