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Cannibal Fish

This is a game for 3-8 players. Players start by choosing different numbers less than 10. This is their initial fish size. Everyone also agrees to the size of fish that will win the game. In this game, Anna, Bob and Clara have agreed that size 51+ wins.

The smallest fish begins by eating one of the other fish. Add that number to their number.

Clara (1) ate Bob's fish (2) and now has 3.

The player with the smallest fish always takes their turn next - so now it is Bob's turn. Bob(2) is going to eat Anna's fish (7). What size will Bob's fish be?

Bob's fish is now size 9. It is Clara's turn since she has the smallest fish. She will eat Bob's fish.

For the first time it's Anna's turn. Anna's fish (7) will eat Clara's fish (12) to create a huge 7+12=19.

Bob's fish will eat Clara's.

Clara's fish (12) chooses to eat Anna's (19) to make it size 31.

Anna can't get to 51! The best she can do is get to 50 by eating Clara's fish.

Bob is going to win by eating either of the other two fish. He chooses to eat Clara's and becomes the first to reach 51.

Bob wins.

Download game boards for three to five players here.

Artists who provide their work for re-use are much appreciated!

Cannibal Fish

(MathPickle, 2015)

Alison Hansel’s class become cannibal fish. Thanks to Alison Hansel, I’ve now added a printable game sheet for three to five players which you can download here.

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)