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20 Dec 2015, 04:47
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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:
45%
(medium)
Question Stats:
62% (01:32) correct
38%
(01:51)
wrong
based on 298
sessions
History
Date
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If the function f is defined for all x by f(x) = ax^2 + bx − 43, where a and b are constants, what is the value of f(3)?
(1) f(4) = 41
(2) 3a + b = 17
(1) f(4) = 41
(2) 3a + b = 17
20 Dec 2015, 22:04
Kudos
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\(F(3) = a*3^2 + b*3 -43 => 9a+3b-43=?\)
I. f(4)=41 =>
\(16a + 4b - 43 =41 => 16a + 4b = 84 or 4a + b = 21\)
Nothing can be done with this information
Not Sufficient
II. 3a + b = 17
\(f(3) = 3 (3a+b) -43 = 3 * 17 - 43\)
Sufficient
Answer is B
I. f(4)=41 =>
\(16a + 4b - 43 =41 => 16a + 4b = 84 or 4a + b = 21\)
Nothing can be done with this information
Not Sufficient
II. 3a + b = 17
\(f(3) = 3 (3a+b) -43 = 3 * 17 - 43\)
Sufficient
Answer is B
21 Dec 2015, 22:30
Kudos
Bookmarks
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
If the function f is defined for all x by f(x) = ax^2 + bx − 43, where a and b are constants, what is the value of f(3)?
(1) f(4) = 41
(2) 3a + b = 17
When you modify the original condition and the question, you only need to know 3a+b from f(3)=a(3^2)+b(3)-43=3(3a+b)-43. 3a+b=17 is in 2), which is unique and sufficient. Therefore, the answer is B.
-> Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.
If the function f is defined for all x by f(x) = ax^2 + bx − 43, where a and b are constants, what is the value of f(3)?
(1) f(4) = 41
(2) 3a + b = 17
When you modify the original condition and the question, you only need to know 3a+b from f(3)=a(3^2)+b(3)-43=3(3a+b)-43. 3a+b=17 is in 2), which is unique and sufficient. Therefore, the answer is B.
-> Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.
