BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Remainder Sum from Manhattan NP Book

Expert replies
by Premalatha Anand » Fri Oct 04, 2013 10:59 am
If X and Y are positive integers and x/y has a remainder of 5, what is the smallest possible value of XY?


Ans is 30
Remainder cannot be larger than Y, so Y should be at least 6.

But my que is how can the smallest possible value of X can be 5??

Please explain!
Regards
Premalatha
Join the discussion
Source: — Problem Solving |

by ceilidh.erickson » Fri Oct 04, 2013 11:05 am
If 5 is divided by 6, the result is 0 remainder 5. The remainder must be smaller than Y, but there's no rule that says that X has to be larger than Y.

If you divide X by a larger integer Y, the result will be 0 remainder X.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
Join the discussion

by Brent@GMATPrepNow » Fri Oct 04, 2013 11:08 am
Premalatha Anand wrote:If X and Y are positive integers and x/y has a remainder of 5, what is the smallest possible value of XY?


Ans is 30
Remainder cannot be larger than Y, so Y should be at least 6.

But my que is how can the smallest possible value of X can be 5??

Please explain!
There a two important rules regarding remainders

#1) If N divided by D, leaves remainder R, then 0 < R < D

#2) If N divided by D, leaves remainder R, then the possible values of N are R, R+D, R+2D, R+3D,. . . etc.

For example, if k divided by 5 leaves a remainder of 1, then the possible values of k are: 1, 1+5, 1+(2)(5), 1+(3)(5), 1+(4)(5), . . . etc.

IMPORTANT: Notice that 1 is the smallest possible value of k. A lot of people miss this. However, 1 divided by 5 equals 0 with remainder 1. In other words, 5 divides into 1 zero times with remainder 1.

For this question, we're told that x divided by y has a remainder of 5. So, the possible values of x are: 5, 5 + y, 5 + 2y, 5 + 3y, 5 + 4y, etc.

So, the SMALLEST value of x is 5.
For the division (x divided by y) leaves a remainder of 5, y must be greater than 5.
So, the SMALLEST value of y is 6

So, the SMALLEST value of xy = (5)(6) = 30

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Join the discussion

by Premalatha Anand » Fri Oct 04, 2013 12:07 pm
Thanks Erickson. Didn't know the rule.

Thanks brent for the detailed explanation!.
Regards
Premalatha
Join the discussion

by vinay1983 » Fri Oct 04, 2013 7:12 pm
Brent@GMATPrepNow wrote:
Premalatha Anand wrote:If X and Y are positive integers and x/y has a remainder of 5, what is the smallest possible value of XY?


Ans is 30
Remainder cannot be larger than Y, so Y should be at least 6.

But my que is how can the smallest possible value of X can be 5??

Please explain!
There a two important rules regarding remainders

#1) If N divided by D, leaves remainder R, then 0 < R < D

#2) If N divided by D, leaves remainder R, then the possible values of N are R, R+D, R+2D, R+3D,. . . etc.

For example, if k divided by 5 leaves a remainder of 1, then the possible values of k are: 1, 1+5, 1+(2)(5), 1+(3)(5), 1+(4)(5), . . . etc.

IMPORTANT: Notice that 1 is the smallest possible value of k. A lot of people miss this. However, 1 divided by 5 equals 0 with remainder 1. In other words, 5 divides into 1 zero times with remainder 1.

For this question, we're told that x divided by y has a remainder of 5. So, the possible values of x are: 5, 5 + y, 5 + 2y, 5 + 3y, 5 + 4y, etc.

So, the SMALLEST value of x is 5.
For the division (x divided by y) leaves a remainder of 5, y must be greater than 5.
So, the SMALLEST value of y is 6

So, the SMALLEST value of xy = (5)(6) = 30

Cheers,
Brent
Brent, does this mean that "R" is always less than D"
You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!
Join the discussion

by Brent@GMATPrepNow » Fri Oct 04, 2013 7:14 pm
vinay1983 wrote: Brent, does this mean that "R" is always less than D"
Yes.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Join the discussion

by [email protected] » Sat Oct 05, 2013 1:22 pm
Hi Premalatha Anand,

I think that all of the other posts in this string have provided the proper insight to answer your initial question, so I'm just going to take a moment to reiterate an important point.

Since "remainder" questions/concepts will usually show up 1-2 times on Test Day, it's worth remembering that remainders are "left over" pieces and the smallest possible numerator in these situations is the one that leads to 0 r <number>.

For example: 3/5 = 0 r 3

Keep this rule in mind any time a "remainder" question appears. It will usually make the question easier to solve.

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Join the discussion

by Premalatha Anand » Sun Oct 06, 2013 8:16 am
Rich,

Easy to remember! Wont forget hereafter. Thanks!
Regards
Premalatha
Join the discussion