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Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
18 Apr 2022, 00:19
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
61% (00:40) correct
39%
(00:42)
wrong
based on 100
sessions
History
Date
Time
Result
Not Attempted Yet
19 Apr 2022, 09:11
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Can somebody explain this why it is not A?
19 Apr 2022, 11:15
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Step 1: Analyse Question Stem
We have to find if a = b. In other words, we have to find if a – b = 0
Step 2: Analyse Statements Independently (And eliminate options) – AD / BCE
Statement 1: ac = bc
A classic trap set up here for test takers who are in the habit of cancelling variables.
Cancelling a certain variable from both sides of the equation is equivalent to dividing the entire equation by that variable.
Remember that there is no mention about the value of c. If c = 0, dividing the equation by c, or in other words, cancelling off c would tantamount to carrying out an operation that is not defined.
Division by ZERO is undefined as far as the GMAT is concerned.
Instead, what GMAT expects you to do in such cases is to use certain standard algebraic processes. Collect all variable terms on one side, factor out terms in common and then use the property of ZERO / property of signs to evaluate the roots.
Given ac = bc, we can transfer bc to the LHS of the equation to get,
ac – bc = 0.
Factoring out c in common, we have,
c (a – b) = 0.
This means that c = 0 OR a -b = 0.
If c = 0, it is not necessary that a be equal to b.
If c ≠ 0, then a = b is necessarily true.
Statement 1 does not give us any information about c.
The data in statement 1 is insufficient to find if a = b.
Statement 1 alone is insufficient. Answer options A and D can be eliminated.
Statement 2: c > 0
Knowing that c > 0 is in no way useful to find out if a = b.
The data in statement 2 is insufficient to find if a = b since no information has been given about these variables.
Statement 2 alone is insufficient. Answer option B can be eliminated.
Step 3: Analyse Statements by combining
From statement 1: c (a – b) = 0
From statement 2: c > 0
Since c ≠ 0, (a – b) = 0.
The combination of statements is sufficient to answer the question, Is a = b, with a definite YES.
Statements 1 and 2 together are sufficient. Answer option E can be eliminated.
The correct answer option is C.
We have to find if a = b. In other words, we have to find if a – b = 0
Step 2: Analyse Statements Independently (And eliminate options) – AD / BCE
Statement 1: ac = bc
A classic trap set up here for test takers who are in the habit of cancelling variables.
Cancelling a certain variable from both sides of the equation is equivalent to dividing the entire equation by that variable.
Remember that there is no mention about the value of c. If c = 0, dividing the equation by c, or in other words, cancelling off c would tantamount to carrying out an operation that is not defined.
Division by ZERO is undefined as far as the GMAT is concerned.
Instead, what GMAT expects you to do in such cases is to use certain standard algebraic processes. Collect all variable terms on one side, factor out terms in common and then use the property of ZERO / property of signs to evaluate the roots.
Given ac = bc, we can transfer bc to the LHS of the equation to get,
ac – bc = 0.
Factoring out c in common, we have,
c (a – b) = 0.
This means that c = 0 OR a -b = 0.
If c = 0, it is not necessary that a be equal to b.
If c ≠ 0, then a = b is necessarily true.
Statement 1 does not give us any information about c.
The data in statement 1 is insufficient to find if a = b.
Statement 1 alone is insufficient. Answer options A and D can be eliminated.
Statement 2: c > 0
Knowing that c > 0 is in no way useful to find out if a = b.
The data in statement 2 is insufficient to find if a = b since no information has been given about these variables.
Statement 2 alone is insufficient. Answer option B can be eliminated.
Step 3: Analyse Statements by combining
From statement 1: c (a – b) = 0
From statement 2: c > 0
Since c ≠ 0, (a – b) = 0.
The combination of statements is sufficient to answer the question, Is a = b, with a definite YES.
Statements 1 and 2 together are sufficient. Answer option E can be eliminated.
The correct answer option is C.
