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CAT 2005 | Question: 16

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Here right most non-zero digit depends on the unit digit of $3^{2720}$

 $3^{2720}$ = $[3^{4}]^{680}$ =$81^{680}$

The unit digit of 81 is 1 so any power of 81 will always give its unit digit as 1.

Thus, required unit digit is 1.

Hence (1).1 is the Answer.
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