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UKMT Senior Mathematical Challenge, 2018

Number theory Difficulty 1.0 Junior Find the answer United Kingdom

Which of the following is not a multiple of 5?

(A) $2019^2-2014^2$ (B) $2019^2\times 10^2$ (C) $2020^2\div 101^2$ (D) $2010^2-2005^2$ (E) $2015^2\div 5^2$

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