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# Which of the following could be the units digit 98^x

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Founder
Joined: 18 Apr 2015
Posts: 6198
Followers: 99

Kudos [?]: 1199 [0], given: 5708

Which of the following could be the units digit 98^x [#permalink]  30 Jul 2017, 08:50
Expert's post
00:00

Question Stats:

48% (00:46) correct 51% (00:55) wrong based on 27 sessions

Which of the following could be the units digit $$98^x$$, where x is an integer greater than 1?

Indicate all such digits:

❑ zero

❑ 1

❑ 2

❑ 3

❑ 4

❑ 5

❑ 6

❑ 7

❑ 8

❑ 9
[Reveal] Spoiler: OA

_________________
GRE Instructor
Joined: 10 Apr 2015
Posts: 1647
Followers: 57

Kudos [?]: 1572 [1] , given: 8

Re: Which of the following could be the units digit 98^x [#permalink]  03 Aug 2017, 15:43
1
KUDOS
Expert's post
Carcass wrote:
Which of the following could be the units digit $$98^x$$, where x is an integer greater than 1?

Indicate all such digits:

❑ zero

❑ 1

❑ 2

❑ 3

❑ 4

❑ 5

❑ 6

❑ 7

❑ 8

❑ 9

[Reveal] Spoiler:
C,E,G,I

98^1 = 98
98^2 = (98)(98) = ---4 [note: we need only recognize that the units digit of 98^2 will be equal to the units digit of (8)(8), which is 4]
98^3 = (98)(98)(98) = (---4)(98) = ----2 [note: we need only recognize that the units digit of (---4)(98) will be equal to the units digit of (4)(8), which is 2]
98^4 = (98)(98)(98)(98) = (----2)(98) = ----6
98^5 = (98)(98)(98)(98)(98) = (----6)(98) = ----8

At this point, we are repeating the pattern. So, there's no need to continue.
The pattern of units digits will be 8, 4, 2, 6, 8, 4, 2, 6, 8, etc

Answer: 2, 4, 6, 8 (C, E, G, I)

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com

Founder
Joined: 18 Apr 2015
Posts: 6198
Followers: 99

Kudos [?]: 1199 [0], given: 5708

Re: Which of the following could be the units digit 98^x [#permalink]  04 Aug 2017, 06:41
Expert's post
Honestly,

I do not think such question adhere to the standards..........
_________________
Re: Which of the following could be the units digit 98^x   [#permalink] 04 Aug 2017, 06:41
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