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What is the remainder of 3^19 when divided by 10? [#permalink]
12 Sep 2014, 11:48
I got D, and this is how I solved: I looked for patterns: ^2 - units digit 9 ^3 - units digit 7 ^4 - units digit 1 ^5 - units digit 3
hence, we can see that when raised to a power which is multiple of 4, the units digit is 1, and when to an even power not multiple of 4, the units digit is 9 and we can then see: ^16 - units digit 1, or ^18 - units digit 9 and ^19 - units digit 7
therefore, when divided by 10, the remainder must be 7
Re: What is the remainder of 3^19 when divided by 10? [#permalink]
14 Nov 2015, 03:06
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