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UKMT Senior Kangaroo, 2020

Algebra Difficulty 1.0 Junior Prove it United Kingdom

What is the difference between the greatest and the least of the following five quantities? $20+20$ , $\; 20 \times 20$ , $\; 20^2+0$ , $\; (2^0)^{(2^0)}$ , $\; 20+2+0$

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