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# Which of the following could be the units digit of where n i

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Moderator
Joined: 18 Apr 2015
Posts: 5152
Followers: 77

Kudos [?]: 1031 [0], given: 4643

Which of the following could be the units digit of where n i [#permalink]  11 Sep 2017, 16:13
Expert's post
00:00

Question Stats:

80% (00:25) correct 20% (00:21) wrong based on 10 sessions
Which of the following could be the units digit of $$57^n$$, where n is a positive integer?

Indicate all such digits.

 0

 1

 2

 3

 4

 5

 6

 7

 8

 9

[Reveal] Spoiler: OA
B,D,H,J

Practice Questions
Question: 4
Page: 123
Difficulty: hard
[Reveal] Spoiler: OA

_________________
Moderator
Joined: 18 Apr 2015
Posts: 5152
Followers: 77

Kudos [?]: 1031 [1] , given: 4643

Re: Which of the following could be the units digit of where n i [#permalink]  11 Sep 2017, 16:21
1
KUDOS
Expert's post
Explanation

$$57^n$$ is the same as $$7^n$$ for the unit digit we care about.

Of course, 7 raised to a power has a repeating pattern

$$7^1=7$$
$$7^2=49$$ unit digit is 9
$$7^3=343$$ unit digit is 3
.........
up to $$7^9$$

The only answer are B,D,H and J
_________________
Re: Which of the following could be the units digit of where n i   [#permalink] 11 Sep 2017, 16:21
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