Question

The rightmost non-zero digit of the number ${30}^{2720}$ is?
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Answer 1

${30}^{2720}=3^{2720}\times {10}^{2720}$
The rightmost non-zero digit of ${30}^{2720}$ will be the digit in the unit's place of $3^{2720}$.
3's power cycle is 3, 9, 7, 1 and cyclicity is 4.
2720 = 680 $\times$ 4
$\therefore$The digit in the unit's place of $3^{2720}$ is 1. $\therefore$The rightmost non-zero digit of ${30}^{2720}$ is 1.