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Q:If a and b are two-digit numbers that share the same [#permalink]
 25 May 2010, 06:47
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Q:If a and b are two-digit numbers that share the same digits, except in reverse order, then what is the sum of a and b? (1) a-b=45 (2) The difference between the two digits in each number is 5. Please explain your answer in detail including why each choice is right or wrong?
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Re: Number Properties - DS [#permalink]
25 May 2010, 07:04
srichaks wrote: Q:If a and b are two-digit numbers that share the same digits, except in reverse order, then what is the sum of a and b? (1) a-b=45 (2) The difference between the two digits in each number is 5. Please explain your answer in detail including why each choice is right or wrong? Any two digit integer n can be expressed as n=10x+y, where x and y are digits, x>0. Given: a=10x+y and b=10y+x. Q: a+b=11(x+y)=?(1) a-b=10x+y-10y-x=45 --> x-y=5. Multiple choices for x and y: (9,4), (8, 3), (7, 2), (6, 1). Not sufficient. (2) x-y=5. Same info as above. Not sufficient. (1)+(2) No new info. Not sufficient. Answer: E.
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Re: Number Properties - DS [#permalink]
25 May 2010, 18:42
Thanks Bunuel!. Great explanation.
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Re: Number Properties - DS [#permalink]
25 May 2010, 21:38
I realized I posted this Q in PS section, Please move this to DS section.
Thanks
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Re: Number Properties - DS [#permalink]
25 May 2010, 22:55
srichaks wrote: Q:If a and b are two-digit numbers that share the same digits, except in reverse order, then what is the sum of a and b? (1) a-b=45 (2) The difference between the two digits in each number is 5. Please explain your answer in detail including why each choice is right or wrong? what does "except in reverse order" signifies here?
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Re: Number Properties - DS [#permalink]
26 May 2010, 02:48
IMO A diffrence betwn two numbers is 45, which is possible only with 49 and 94
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Re: Number Properties - DS [#permalink]
26 May 2010, 04:24
IMO is E.
Not A since even difference between 61 and 16 gives 45.
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Re: Number Properties - DS [#permalink]
29 May 2010, 07:09
I dont understand the "except in reverse order" part???????
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Re: Number Properties - DS [#permalink]
29 May 2010, 07:20
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Re: Number Properties - DS [#permalink]
30 May 2010, 06:27
Bunuel wrote: hardnstrong wrote: I dont understand the "except in reverse order" part??????? It means that if digits in a are xy, then in b the digits are yx (in reverse order). According to the solution above there are 5 pairs of a and b possible satisfying both statements (94 and 49, 83 and 38, 72 and 27, 61 and 16). So multiple answer to a+b. Not sufficient. Hope it's clear. This is the confusing part in this question............ except in reverse order means they cannot be in reverse order (so if a = xy then b cannot be yx) Dont you think "except in reverse order" takes question is completely different direction, or should it be "in reverse order"
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Re: Number Properties - DS [#permalink]
30 May 2010, 06:40
hardnstrong wrote: Bunuel wrote: hardnstrong wrote: I dont understand the "except in reverse order" part??????? It means that if digits in a are xy, then in b the digits are yx (in reverse order). According to the solution above there are 5 pairs of a and b possible satisfying both statements (94 and 49, 83 and 38, 72 and 27, 61 and 16). So multiple answer to a+b. Not sufficient. Hope it's clear. This is the confusing part in this question............ except in reverse order means they cannot be in reverse order (so if a = xy then b cannot be yx) Dont you think "except in reverse order" takes question is completely different direction, or should it be "in reverse order" Not a perfect wording - agree. "except in reverse order" here means "but in reverse order".
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PLEASE READ AND FOLLOW: 11 Rules for Posting!!!
RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory
COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. NEW!!!
DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set. NEW!!!
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Re: Number Properties - DS
[#permalink]
30 May 2010, 06:40
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