Maybe a poor example, some questions like this say: (7^243)+(7^22)-5 divided by 7, what is the remainder?
How to solve this kind of problem?
Thanks
About remainder question
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 60
- Joined: Tue Feb 08, 2011 8:55 pm
- Location: Canada
- Thanked: 7 times
- GMAT Score:700
I think it's important to look at the terms and how they fit to solve this question.
(7^243)+(7^22)-5 divided by 7 = [ (7^243) + (7^22) - 5 ] / 7
This expression can be broken down further by dividing 7 into each term.
(7^243)/7 + (7^22)/7 - 5/7
The 1/7 term seemlessly goes into the 7^243 and 7^22 term, because 1/7 = 7^(-1), i.e. two numbers with the same base (7) are being multiplied. This means there is no remainder.
The - 5 term isn't so fortunate. 7 is too big to be to divided into 5, so 5 is the remainder.
(7^243)+(7^22)-5 divided by 7 = [ (7^243) + (7^22) - 5 ] / 7
This expression can be broken down further by dividing 7 into each term.
(7^243)/7 + (7^22)/7 - 5/7
The 1/7 term seemlessly goes into the 7^243 and 7^22 term, because 1/7 = 7^(-1), i.e. two numbers with the same base (7) are being multiplied. This means there is no remainder.
The - 5 term isn't so fortunate. 7 is too big to be to divided into 5, so 5 is the remainder.
GMAT/MBA Expert
- Anurag@Gurome
- GMAT Instructor
- Posts: 3835
- Joined: Fri Apr 02, 2010 10:00 pm
- Location: Milpitas, CA
- Thanked: 1854 times
- Followed by:523 members
- GMAT Score:770
(7^243) + (7^22) - 5 = (Some multiple of 7) - 5neilcao wrote:(7^243)+(7^22)-5 divided by 7, what is the remainder?
Now any integer less than a multiple of 7 by 5, when divided by 7 will leave a remainder of (7 - 5) = 2
Because, 7k - 5 = 7(k - 1) + 7 - 5 = 7(k - 1) + 2
Where k is any positive integer.
Note: If the expression was (7^243) + (7^22) + 5, then the remainder would've been 5.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)
Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)
Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/