Stage: 3 and 4 Challenge Level: 
What can you deduce by comparing the bottom two rows?
If you could work out the value of the square, how could you then work out the value of the triangle?
Quadratic equations. Working systematically. Mathematical reasoning & proof. Simultaneous equations. Live - Secondary. Stage 5 - Core Mapping. smartphone. Using symbols. Trial and improvement. Manipulating algebraic expressions/formulae.
Published April 2001,November 2011,December 2011.
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