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# Unit's digit of large factorials with exponents?

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Intern
Joined: 03 Nov 2017
Posts: 1
Unit's digit of large factorials with exponents?  [#permalink]

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23 Nov 2017, 02:04
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (00:00) wrong based on 1 sessions

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if

$$\frac{((13!)^{16} -(13!)^8)}{(13!)^8+(13!)^4}$$ = a

then what is the unit's digit of $$\frac{a}{(13!)^4}$$

A) 0
B) 1
C) 3
D) 5
E) 9

Any input is appreciated, since I don't even know where to start on this one.

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Math Expert
Joined: 02 Sep 2009
Posts: 50041
Re: Unit's digit of large factorials with exponents?  [#permalink]

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23 Nov 2017, 02:08
sebcroy wrote:
if

$$\frac{((13!)^{16} -(13!)^8)}{(13!)^8+(13!)^4}$$ = a

then what is the unit's digit of $$\frac{a}{(13!)^4}$$

A) 0
B) 1
C) 3
D) 5
E) 9

Any input is appreciated, since I don't even know where to start on this one.

Discussed here: if-a-13-1-6-13-8-13-8-13-4-hat-is-the-unit-digit-of-165186.html Hope it helps.

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

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Re: Unit's digit of large factorials with exponents? &nbs [#permalink] 23 Nov 2017, 02:08
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