The rightmost non-zero digit of the number 302720 is
a) 1
b) 3
c) 7
d) 9
Answer: a
Explanation: (30)2720, we can write it as[(30)4]680
= [(10 × 3)4]680
The right most non-zero digit depends on the unit digit of [(3)4]680
Unit digit of [(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
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