What is the unit's digit of $a^{18}$?

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VJesus12: Legendary Member; Posts: 2276; Joined: Sat Oct 14, 2017 6:10 amFollowed by: 3 members

by VJesus12 » Sat Nov 23, 2019 2:21 am

What is the unit's digit of $a^{18}$?

(1) $a^2$ has a units digit of 9
(2) $a^7$ has a units digit of 3

[spoiler]OA=D[/spoiler]

Source: Veritas Prep

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Source: Beat The GMAT — Data Sufficiency | Sat Nov 23, 2019 2:21 am

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