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Lazy Lemur Multiplication

Let's start with an example. 01746 is good for lazy lemur multiplication because you can multiply it by a digit greater than one so that all five digits get shuffled, but remain the same. 

Students are lazy lemurs.  As soon as they discover that a product produces an incorrect digit, they should stop and try multiplying with a different number...

Printable puzzle-sheets here.

Does this work?

No! The result is that 01746 multiplied by two does not end up with the digits 0,1,7,4,6 shuffled. There is a 2, 3 and 9.

It is important that the students not complete the multiplication as I have done on the left. They should stop as soon as they find an incorrect digit. The reason is twofold...

1) It is fun to call the lemur's (your students) lazy. This adds to the story and to the fun.

2) By forcing students to stop (and be lazy) if they see an incorrect digit, you are creating the good habit of getting students to think as they are performing an algorithm. Too often algorithms are applied without thought.

Students do not have to be methodical, but you may choose to congratulate a student that systematically searches for the digit 2-9 to multiply 01746. Here I've decided not to be systematics. Does 5 work?

Alas - 5 does not work either.

Does 6 work?

Yes! This produces a shuffling of the digits 0,1,7,4, and 6.

I'll leave you with one other puzzle - a lot more are to be found on the puzzle-sheets that can be downloaded on the first slide.

The answer here must shuffle the digits 1,0,9,8,9 so the answer will have two nines.

Enjoy encouraging your class to be lazy!

Lazy Lemur Puzzles

(MathPickle, 2014)

These photos are from the lazy students in Alison Hansel’s and Joli Barker’s math classes. They were just waiting for an excuse to terminate their calculations 😉

Standards for Mathematical Practice

MathPickle puzzle and game designs engage a wide spectrum of student abilities while targeting the following Standards for Mathematical Practice:

MP1 Toughen up!

Students develop grit and resiliency in the face of nasty, thorny problems. It is the most sought after skill for our students.

MP2 Think abstractly!

Students take problems and reformat them mathematically. This is helpful because mathematics lets them use powerful operations like addition.

MP3 Work together!

Students discuss their strategies to collaboratively solve a problem and identify missteps in a failed solution. MathPickle recommends pairing up students for all its puzzles.

MP4 Model reality!

Students create a model that mimics the real world. Discoveries made by manipulating the model often hint at something in the real world.

MP5 Know the tools.

Students master the tools at their fingertips - whether it's a pencil or an online app. 

MP6 Be precise!

Students learn to communicate using precise terminology. MathPickle encourages students not only to use the precise terms of others, but to invent and rigorously define their own terms.

MP7 Be observant!

Students learn to identify patterns. This is one of the things that the human brain does very well. We sometimes even identify patterns that don't really exist 😉

MP8 Be lazy!?!

Students learn to seek for shortcuts. Why would you want to add the numbers one through a hundred if you can find an easier way to do it?


Please use MathPickle in your classrooms. If you have improvements to make, please contact me. I'll give you credit and kudos 😉 For a free poster of MathPickle's ideas on elementary math education go here.

Gordon Hamilton

(MMath, PhD)