Licorice Triangles
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 Here's an idea that's sure to keep students interested.

1.  Divide students into groups of three for this exercise.
2.  Give each group a
generous supply of licorice shoe laces.
3.  Give each group a set of rulers. 
4.  Have the students cut (or rip) the licorice into specific lengths
    
(even numbers from 2 to 20 work well.)  

5 .  After ripping or cutting the licorice strips, the excess can be eaten.
     
(Students consider this to be the best part of the activity.)
6.  Have students attempt to create triangles from their measured pieces.
7.  Students will make a chart to keep track of their data, noting the lengths of the sides, and whether or not these lengths formed a triangle.

8.  Be sure that the groups work with various lengths in their attempts to form triangles.  Each group should work until they have 3 examples where the sides formed triangles and 3 examples where the sides did NOT form triangles.

9.  Ask students to compare their examples and try to form a conjecture about the inequality relationship involving the sides of a triangle.  Some students may need hints, but many students will come up with the relationship.

Students can also discover the inequality relationship among the sides and angles in a triangle in a similar manner.  For this extension activity, students will need protractors to measure the angles.

 

As an added incentive for the students to discover the theorems, you could tell them NOT to eat the excess licorice until the theorems have been discovered.  This may, however, be difficult to enforce.