## No three in a line puzzle

### (Henry Dudeney, 1917)

This is a great idea to get your students thinking about patterns. Watch the video above first.

There are some changes that improve the experience:

1) I now start the class by getting them to solve the 3x3 city with six skyscrapers. Persist until it is solved. Then I start them out on the 4x4, but aim for a classroom failure before releasing them to solve the 4x4 puzzle in pairs.

2) Although manipulatives (like the ones you see being used in the video above) have big advantages, I like student work to be preserved over time, so I now use pen and paper. I say “pen and paper” rather than “pencil and paper,” because students should get into the habit of preserving and learning from their mistakes – not erasing them.

Download the pdf of the 4x4 and 6x6 puzzle sheets here.

To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is to work out what aliens might actually be like.

**Stephen Hawking**

**Standards for ****Mathematical Practice**

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

#### MP1 Toughen up!

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

##### MP3 Work together!

This is collaborative problem solving in which students discuss their strategies to solve a problem and identify missteps in a failed solution. MathPickle recommends pairing up students for all its puzzles.

##### MP6 Be precise!

This is where our 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!

One of the things that the human brain does very well is identify pattern. We sometimes do this too well and identify patterns that don’t really exist.