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Which of the following could be the units digit 98^x
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30 Jul 2017, 08:50
30 Jul 2017, 08:50
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Question Stats:
44% (01:03) correct
55% (01:10) wrong based on 121 sessions
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Which of the following could be the units digit \(9^{8^x}\), where x is an integer greater than 1?
Indicate all such digits:
❑ zero
❑ 1
❑ 2
❑ 3
❑ 4
❑ 5
❑ 6
❑ 7
❑ 8
❑ 9
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Official Answer
C,E,G,I
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: Which of the following could be the units digit 98^x
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03 Aug 2017, 15:43
03 Aug 2017, 15:43
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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
Indicate all such digits:
❑ zero
❑ 1
❑ 2
❑ 3
❑ 4
❑ 5
❑ 6
❑ 7
❑ 8
❑ 9
Show: ::
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
Re: Which of the following could be the units digit 98^x
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04 Aug 2017, 06:41
04 Aug 2017, 06:41
Expert Reply
Honestly,
I do not think such question adhere to the standards..........
I do not think such question adhere to the standards..........
