5^100 is divided by 18 then what is the remainder?
Select
A) 10
B) 11
C) 13
D) 15
E) 16
Here N = 18=2×32   ϕ(18)=18(1−12)(1−13) = 6   So 56 when divided by 18, remainder is 1.   So we can write the given expression 5100=(56)16×54 = (1)16×54 = 52×52=7×7=49   Now 49 when divided by 18, remainder is 13.   13
<result>C</result>
5^100 is divided by 18 then what is the remainder?