Stage: 3 and 4 Challenge Level: 
If you are a teacher, click here for a version of the problem suitable for classroom use, together with supporting materials. Otherwise, read on...
Each symbol has a numerical value. The total for the symbols is written at the end of each row and column.
Can you find the missing total that should go where the question mark has been put?
Once you've had a go at the problem, click below to see how Charlie, Alison and their friends began working on the task.
Can you take each of their starting points and develop them into a solution?
Method 1
Method 2
Method 3
Method 4
Method 5
Method 6
Method 7
Method 8
Can you find any other methods to solve the problem?
You can apply these methods to other versions of the problem. This spreadsheet can be used to generate lots of different examples.
To discuss the different methods, or others
you may have come up with yourself, visit the blog
Here are three other problems that can be solved using similar strategies:
Manipulating algebraic expressions/formulae. Trial and improvement. Live - Secondary. Stage 5 - Core Mapping. Using symbols. smartphone. Working systematically. Mathematical reasoning & proof. Quadratic equations. Simultaneous equations.
Published April 2001,November 2011,December 2011.
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