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27 Jan 2020, 02:51
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
86% (01:01) correct
14%
(01:00)
wrong
based on 77
sessions
History
Date
Time
Result
Not Attempted Yet
If a, b are positive integers, what is the value of b?
(1) \(2^a7^b=1,372\)
(2) \(a=2\)
(1) \(2^a7^b=1,372\)
(2) \(a=2\)
27 Jan 2020, 03:12
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Statement 1 alone is sufficient
2^2 7^3 = 1372
a=2; b=3
Posted from my mobile device
2^2 7^3 = 1372
a=2; b=3
Posted from my mobile device
27 Jan 2020, 20:58
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Bunuel
Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.
Visit https://www.mathrevolution.com/gmat/lesson for details.
The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question. We should simplify conditions if necessary.
Condition 1)
Since \(2^a \cdot 7^b = 1372 = 2^2 \cdot 7^3\), we have \(a = 2\) and \(b = 3\).
Since condition 1) yields a unique solution, it is sufficient.
Condition 2)
Since there is no information about the variable \(a\) in condition 2), condition 2) is not sufficient obviously.
Therefore, A is the answer.
