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, 2015

Number theory Difficulty 1.0 Junior Prove it United Kingdom

What is the units digit in the answer to the sum $9^{2015} + 9^{2016}$ ?

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Source: UK Mathematics Trust, licensed © UK Mathematics Trust; past papers published free at ukmt.org.uk. Statement reproduced verbatim; metadata (topic, difficulty) added by this project. Solutions are the publisher's, linked not copied.