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Isosceles
Age 11 to 14
Challenge Level 
Prove that a triangle with sides of length 5, 5 and 6 has the same area as a triangle with sides of length 5, 5 and 8.
Find other pairs of isosceles triangles which are not congruent but have equal areas.
How many isosceles triangles have an area of 12 square units?
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