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Pat pat pat

Number Theory Level 1

Consider the following pattern:

$\begin{array} {l r} \\ 5 ^ 1 = & 5 \\ 5^2 = & 25 \\ 5^3 = & 125 \\ 5^4 = & 625 \\ \end{array}$

What is the units digit of $5^{25}$ ?

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by Arron Kau

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