(integer) What is the remainder when 7^442 is divided by 10?

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Max@Math Revolution: Elite Legendary Member; Posts: 3991; Joined: Fri Jul 24, 2015 2:28 amFollowed by: 37 members; Location: Las Vegas, USA; Thanked: 19 times

by Max@Math Revolution » Thu Sep 22, 2016 4:20 pm

(integer) What is the remainder when 7442 is divided by 10?
A. 1 B. 3 C. 5 D. 7 E. 9

Last edited by Max@Math Revolution on Sat Sep 24, 2016 9:23 pm, edited 1 time in total.

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16206; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Fri Sep 23, 2016 4:50 am

Max@Math Revolution wrote:(integer) What is the remainder when 7442 is divided by 10?
A. 1 B. 3 C. 5 D. 7 E. 9

Are you sure you've correctly transcribed the question? As it stands, the correct answer is 2

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Brent

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regor60: Master | Next Rank: 500 Posts; Posts: 416; Joined: Thu Oct 15, 2009 11:52 am; Thanked: 27 times

by regor60 » Fri Sep 23, 2016 7:33 am

I guess it could 1 since 2/10 reduces to 1/5

Max@Math Revolution: Elite Legendary Member; Posts: 3991; Joined: Fri Jul 24, 2015 2:28 amFollowed by: 37 members; Location: Las Vegas, USA; Thanked: 19 times

by Max@Math Revolution » Sat Sep 24, 2016 9:23 pm

==> From, ~71=~7, ~72=~9, ~73=~3, ~74=~1, the first digit has a cycle of ^4 in the order of 7-->9-->3-->1-->7. If so, from 442=4*110+2 you get the remainder of 2, and you get 7442=74*110+2=~72=~9. Hence, the answer is E.
Answer: E

- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16206; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sun Sep 25, 2016 7:06 am

Max@Math Revolution wrote:==> From, ~71=~7, ~72=~9, ~73=~3, ~74=~1, the first digit has a cycle of ^4 in the order of 7-->9-->3-->1-->7. If so, from 442=4*110+2 you get the remainder of 2, and you get 7442=74*110+2=~72=~9. Hence, the answer is E.
Answer: E

- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

Once you post a question/reply, you might consider checking the post to ensure that the formatting is correct.
I believe that 71, 72, 73 etc are meant to be expressed as 7^1, 7^2, 7^3 etc

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

regor60: Master | Next Rank: 500 Posts; Posts: 416; Joined: Thu Oct 15, 2009 11:52 am; Thanked: 27 times

by regor60 » Sun Sep 25, 2016 12:41 pm

Max@Math Revolution wrote:==> From, ~71=~7, ~72=~9, ~73=~3, ~74=~1, the first digit has a cycle of ^4 in the order of 7-->9-->3-->1-->7. If so, from 442=4*110+2 you get the remainder of 2, and you get 7442=74*110+2=~72=~9. Hence, the answer is E.
Answer: E

- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

Once again, and I'm not trolling, you've posed an improperly expressed problem.

In other words, this isn't the first time.

You hold yourself out as a math "expert", but your expertise seems to lie in wasting people's time.

regor60: Master | Next Rank: 500 Posts; Posts: 416; Joined: Thu Oct 15, 2009 11:52 am; Thanked: 27 times

by regor60 » Sun Sep 25, 2016 12:41 pm

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