CAT 2005 Question Paper Question 16

Question 16

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

Solution

Rightmost non-zero digit of $$30^{2720}$$ is same as rightmost non-zero digit of $$3^{272}$$.

272 is of the form 4k.

All $$3^{4k}$$ end in 1.

=> Right most non-zero digit is 1.



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