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 Post subject: Algebra: Applied Problems
PostPosted: Thu Feb 04, 2010 11:23 am 
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Joined: Thu Dec 31, 2009 9:45 am
Posts: 1
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.) 165
C.) 121
D.) 99
E.) 44

Answer: It is given that M and N have the same digits in reverse order. Let M=10t+u and N=10u+t, where t and u are two digits. Then, M+N= (10t+u) + (10u+t) = 11(t+u). This means that any sum of the two integers M and N must also be a multiple of 11. Of the answer choices, only 181 is not a multiple of 11 and thus cannot be the sum of M and N

HELP!!!! I do not understand where the author came up with the number 10. Why 10t and 10u? please help, I understand that 181 is not a multiple of 11 and the rest are, hence the correct answer: but I do not understand the reasoning!


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 Post subject: Re: Algebra: Applied Problems
PostPosted: Mon Apr 12, 2010 10:12 pm 
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Joined: Mon Apr 12, 2010 10:08 pm
Posts: 1
t and u are single digits 0-9, so 10t + u makes a 2 digit number,

ie. if t=2 and u=4, 10t + u=24


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