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What is the unit digit of 4387^245*621^72 ?
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04 Jul 2022, 12:45
04 Jul 2022, 12:45
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Expert Reply
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00:00
A
B
C
D
E
Difficulty:
5%
(low)
Question Stats:
85% (00:49) correct
15%
(01:27)
wrong
based on 97
sessions
What is the unit digit of \(4387^{245}*621^{72}\) ?
(A) 1
(B) 2
(C) 5
(D) 7
(E) 8
(A) 1
(B) 2
(C) 5
(D) 7
(E) 8
Re: What is the unit digit of 4387^245*621^72 ?
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04 Jul 2022, 16:10
04 Jul 2022, 16:10
Expert Reply
This question is recurrent in the GMAT official guide books.
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5ADD57AA-E7AB-462E-8C55-41F21EC297DB.jpeg [ 231.91 KiB | Viewed 2071 times ]
What is the unit digit of 4387^245*621^72 ?
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04 Jul 2022, 16:15
04 Jul 2022, 16:15
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Expert Reply
Bunuel
What is the unit digit of \(4387^{245}*621^{72}\) ?
(A) 1
(B) 2
(C) 5
(D) 7
(E) 8
(A) 1
(B) 2
(C) 5
(D) 7
(E) 8
Units digit of 621^anything is 1, so we can just ignore that part.
\(4387^{245}\)
7^something cycles 7, 9, 3, 1. B, C, and E are out.
Is 245 a multiple of 4? Nope. A is out.
Answer choice D.
