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What is the units digit of 2^39?

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What is the units digit of 2^39? [#permalink]

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New post 25 Feb 2017, 19:35
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What is the units digit of 2^39?

A) 2
(B) 4
(C) 6
(D) 8
(E) 9
[Reveal] Spoiler: OA
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Re: What is the units digit of 2^39? [#permalink]

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New post 25 Feb 2017, 23:03
vikasp99 wrote:
What is the units digit of 2^39?

A) 2
(B) 4
(C) 6
(D) 8
(E) 9


\(2^1 = 2\)
\(2^2 = 4\)
\(2^3 = 8\)
\(2^4 = 16\)

\(2^5 = 32\)


Thus, the cyclicity of units digit 2 is 4...


Now, \(2^{39} = 2^{36}*2^3\)

Or, \(2^{39} = 2^{4*9}*2^3\)

\(2^{39} = 6*8\) ( As 2^4 = Units digit 6 ) & ( 2^3 = Units digit 8 )

Thus, the units digit of 2^{39} = 8

Hence, the answer must be (D) 8
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Thanks and Regards

Abhishek....

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Re: What is the units digit of 2^39?   [#permalink] 25 Feb 2017, 23:03
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What is the units digit of 2^39?

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