Unit digit

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Captchar: Junior | Next Rank: 30 Posts; Posts: 15; Joined: Sun Dec 16, 2012 4:04 am

by Captchar » Sun Dec 16, 2012 4:49 am

The unit digit of 2^34 x 3^45 x 4^56 x 5^67 x 6^78 x 7^89 is
A) 0
B) 1
C) 2
D) 3
E) 4

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Source: Beat The GMAT — Problem Solving | Sun Dec 16, 2012 4:49 am

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Sun Dec 16, 2012 4:51 am

Captchar wrote:The unit digit of 2^34 x 3^45 x 4^56 x 5^67 x 6^78 x 7^89 is

The given product is multiple of 2 and 5, i.e multiple of 10.
Hence, the unit's digit of the product is 0.

The correct answer is A.

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Jim@StratusPrep: MBA Admissions Consultant; Posts: 2279; Joined: Fri Nov 11, 2011 7:51 amFollowed by: 266 members; Location: New York; Thanked: 660 times; GMAT Score:770

by Jim@StratusPrep » Mon Dec 17, 2012 4:42 pm

Always look for a short step with these long problems... 5 x 2 = 10 so the ones digit will always be 0.

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