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GMAT Paper Test (Code 25, Q#14)

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by Nisha1218 » Fri Sep 07, 2007 5:59 am
If the two-digit integers M and N are positive and have the same digits, but in reverse order, which of the following CANNOT be the sum of M and N?

A. 181
B. 16
C. 121
D. 99
E. 44

Please help! Thanks.
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by givemeanid » Fri Sep 07, 2007 6:25 am
Sum of those two numbers will be a multiple of 11. So, the answer would be any number that is not a multiple of 11.
So It Goes
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by samirpandeyit62 » Fri Sep 07, 2007 6:32 am
let M be "ab"

so N will be "ba"

hence we can say M = 10a + b

and N =10b + a

so M + N = 11a +11b

hence it is 11(a + b)

i.e sum will be 11 * (sum of the 2 digits)
hence it is a multiple of 11

but I see in the answers there are 3 choice which are muliples of 11

and 2 choices which are not i.e 16, 181

are u sure that there is no typo in the choices.

Regards
Samir
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by ri2007 » Fri Sep 07, 2007 7:34 am
samirpandeyit62

i got the same answer as you - but I used instinct, POE and some plugging in to get there.

Should have used the equation instead - much faster and more reliable. Really appreciate your posts - am becoming a fan :)
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by Nisha1218 » Fri Sep 07, 2007 8:24 am
Choice B should be stated as 165 which is also a multiple of 11.
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by samirpandeyit62 » Fri Sep 07, 2007 8:26 am
Thanks ri2007 for your compliments, but I dont really think I'm better than you or the many brilliant people around here, just trying to learn & extend any possible help from my side, Knowlege increases by sharing, I'm sharning mine & trying to gain from others over here. Thats how I look at it.

Thanks
Samir
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