Stage: 4 Challenge Level: 
Is it always the case that when you square a number whose last digit is 5 you always end with 25?
By breaking the number down into a form (x + 5) it may then be possible to see what is happening and why.
Modulus arithmetic. Stage 5 - Reviewed 2012. Manipulating algebraic expressions/formulae. Factors and multiples. Number theory. Properties of numbers. Mathematical reasoning & proof. Polynomials. Place value. Index notation/Indices.
Published September 2002.
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