Even I got C. Not sure what am I missing.nroy347 wrote:If a^2b^2c^3 = 4500 . Is b+c = 7 ?
(1) a, b and c are positive integers
(2) a > b
after i solved . i got C, however the answer shown was E.Can anyone explain this...
Exponents..Numbers
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vk_vinayak
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neelgandham
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Interesting!
If a^2 * b^2 * c^3 = 4500. Is b+c = 7?
Case 1: a^2 * b^2 * c^3 = 2^2 * 3^2 * 5^3
a = 2, b = 3 and c = 5.
Is b+c=7 ? No! b+c = 3+5 = 8.
Case 2: a^2 * b^2 * c^3 = 3^2 * 2^2 * 5^3
a = 3, b = 2 and c = 5.
Is b+c=7 ? Yes! b+c = 2+5 = 7.
I am sure that you might have considered the above cases BUT(and a big one) did you consider the case where the value of a or b is 1?
Case 3: a^2 * b^2 * c^3 = 6^2 * 1^2 * 5^3
a = 6, b = 1 and c = 5.
Is b+c=7 ? No! b+c = 1+5 = 6.
Case 3: a^2 * b^2 * c^3 = 1^2 * 6^2 * 5^3
a = 1, b = 6 and c = 5.
Is b+c=7 ? No! b+c = 6+5 = 11.
Since we don't have a definite answer, statement I is insufficient to answer the question.
Since we don't have a definite answer, statement II is insufficient to answer the question.
Case 2: a^2 * b^2 * c^3 = 3^2 * 2^2 * 5^3
a = 3, b = 2 and c = 5.(a>b)
Is b+c=7 ? Yes! b+c = 2+5 = 7.
Case 3: a^2 * b^2 * c^3 = 6^2 * 1^2 * 5^3
a = 6, b = 1 and c = 5.(a>b)
Is b+c=7 ? No! b+c = 1+5 = 6.
Since we don't have a definite answer, [Statement I + Statement II]-combined isn't sufficient to answer the question.
Answer E
If a^2 * b^2 * c^3 = 4500. Is b+c = 7?
a^2 * b^2 * c^3 = 4500(1) a, b and c are positive integers
Case 1: a^2 * b^2 * c^3 = 2^2 * 3^2 * 5^3
a = 2, b = 3 and c = 5.
Is b+c=7 ? No! b+c = 3+5 = 8.
Case 2: a^2 * b^2 * c^3 = 3^2 * 2^2 * 5^3
a = 3, b = 2 and c = 5.
Is b+c=7 ? Yes! b+c = 2+5 = 7.
I am sure that you might have considered the above cases BUT(and a big one) did you consider the case where the value of a or b is 1?
Case 3: a^2 * b^2 * c^3 = 6^2 * 1^2 * 5^3
a = 6, b = 1 and c = 5.
Is b+c=7 ? No! b+c = 1+5 = 6.
Case 3: a^2 * b^2 * c^3 = 1^2 * 6^2 * 5^3
a = 1, b = 6 and c = 5.
Is b+c=7 ? No! b+c = 6+5 = 11.
Since we don't have a definite answer, statement I is insufficient to answer the question.
So? Irrelevant.(2) a > b
Since we don't have a definite answer, statement II is insufficient to answer the question.
The value of a is greater than b in two cases, case 2 and case 3:](1) a, b and c are positive integers PLUS (2) a > b
Case 2: a^2 * b^2 * c^3 = 3^2 * 2^2 * 5^3
a = 3, b = 2 and c = 5.(a>b)
Is b+c=7 ? Yes! b+c = 2+5 = 7.
Case 3: a^2 * b^2 * c^3 = 6^2 * 1^2 * 5^3
a = 6, b = 1 and c = 5.(a>b)
Is b+c=7 ? No! b+c = 1+5 = 6.
Since we don't have a definite answer, [Statement I + Statement II]-combined isn't sufficient to answer the question.
Answer E
Anil Gandham
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vk_vinayak
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adthedaddy
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Nice explanation Anil. Thanks for giving a wholistic view to the problem 
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neelgandham
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Thanks all!
Most of the times we ignore to consider integers 1,0 and -1, if the variable used in the question is an integer. We also tend to assume that a variable is an integer and keep looking for possible integer solutions.
In order to avoid such mistakes you SHOULD
a) Practice a lot.
b) Read the question carefully.
c) Never assume.
Most of the times we ignore to consider integers 1,0 and -1, if the variable used in the question is an integer. We also tend to assume that a variable is an integer and keep looking for possible integer solutions.
In order to avoid such mistakes you SHOULD
a) Practice a lot.
b) Read the question carefully.
c) Never assume.
Anil Gandham
Welcome to BEATtheGMAT | Photography | Getting Started | BTG Community rules | MBA Watch
Check out GMAT Prep Now's online course at https://www.gmatprepnow.com/
Welcome to BEATtheGMAT | Photography | Getting Started | BTG Community rules | MBA Watch
Check out GMAT Prep Now's online course at https://www.gmatprepnow.com/
