Which One Doesn't Belong?

While scrolling through some education tweets this week, I came across a math site called "Which One Doesn't Belong?" found at wodb.ca.  On the site can be found puzzles with a picture in each of four quadrants.

Shape #1

To launch our geometry unit, I thought to start with the above puzzle.  This would let me know where the students were in terms of attributes of polygons.  Which one doesn't belong?  Here are some thoughts from the grade sixes on Day 1 of Geometry. 

Bottom Right:

--it's grey and others are white--Allyssa

--seems smaller than the others--Andre

--it's the only one with a right angle--Gabriella

--perimeter of 69 cm

Bottom Left:

--no equal sides (Scalene?) --Gloria

Top Right:

--this is a hexagon and the others are triangles--Gabriella

--parallel lines--Max

--all equal sides

--only has obtuse angles--Gloria

Top Left:

--this one sits on its vertex but the others are on an edge--Xavier

What I liked about this site is that it doesn't post answers!  Part of growing in math confidence this year is allowing for time and making mistakes and not having just one "right" answer.  This is thrilling for a math learner and educator.  If you look at the sophistication of some of the answers, they vary from beginner to higher end.  BUT EVERYONE CAN PARTICIPATE!

Take Allyssa's observation that the one shape is grey.  She is not wrong.  She has contributed to the group's discussion.  She's participated.  This is a PLUS.  The next time we did a puzzle, a different student made the observation about the difference in colour which led to the wonder "does the colour of the object affect the math?" to which the students replied "no, but she's not wrong".  SUCCESS!

Something else that came from this puzzle was the math language.  Students seemed to dig deep into their "backpacks" of knowledge to come up with innovative and original observations.  You might notice the lines of symmetry drawn on the shapes because that also became a discussion as the class worked together to discover the lines of symmetry for each polygon.  One student wondered if the lines of symmetry had to do with the number of sides.  Since three of the shapes were triangles, that logic meant that all the triangles had 3 lines of symmetry.  BUT, only the triangle with EQUAL sides had 3 lines of symmetry.  A great discovery!

Try WODB in your class and let us know what you see happening in your class.

~MissBrooks