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05 May 2021, 05:00
Kudos
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
63% (00:57) correct
37%
(01:20)
wrong
based on 110
sessions
History
Date
Time
Result
Not Attempted Yet
If a^2 + b^2 = 41, what is the value of (a − b)^2 ?
(1) a = 5
(2) ab = −20
(1) a = 5
(2) ab = −20
05 May 2021, 05:08
Kudos
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\((a-b)^2\) = \(a^2 \)+ \(b^2\) - 2ab = 41 - 2ab
We need to find the value of ab
S1) a=5
The value of b is not provided, hence ab cannot be found.
Not sufficient.
S2) ab = -20
Hence, \((a-b)^2\) = 41-(-40) = 81
Sufficient.
The answer will be B.
We need to find the value of ab
S1) a=5
The value of b is not provided, hence ab cannot be found.
Not sufficient.
S2) ab = -20
Hence, \((a-b)^2\) = 41-(-40) = 81
Sufficient.
The answer will be B.
05 May 2021, 05:16
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Bunuel
Given: a² + b² = 41
Target question: What is the value of (a − b)² ?
This is a good candidate for rephrasing the target question.
(a − b)² = (a − b)(a − b)
(a − b)² = a² - 2ab + b²
(a − b)² = a² + b² - 2ab
Since we're told a² + b² = 41, we get: (a − b)² = 42 - 2ab
So, in order to determine the value of (a − b)², we need only find the value of 2ab
REPHRASED target question: What is the value of 2ab?
Statement 1: a = 5
Since we have no information about the value of b, there's no way to answer the REPHRASED target question with certainty
Statement 1 is NOT SUFFICIENT
Statement 2: ab = −20
If ab = −20, then 2ab = −40
Since we can answer the REPHRASED target question with certainty, statement 2 is SUFFICIENT
Answer: B
Cheers,
Brent
VIDEO ON REPHRASING THE TARGET QUESTION:
