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E
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:
75% (01:10) correct
25%
(01:20)
wrong
based on 59
sessions
History
Date
Time
Result
Not Attempted Yet
If bot a and b are nonzero integers, what is the value of a*b ?
(1) a^2=b^2
(2) \(\sqrt{b}=2\)
(1) a^2=b^2
(2) \(\sqrt{b}=2\)
1) \(a^2\) \(-\) \(b^2\) \(=\) \(0\) ---> \((a - b)\) \((a + b)\) \(=\) \(0\) ----> \(a = b\)and \(a= -b\) insuff
2) \(b = 2\) ---> basically \(\sqrt{b}\) \(=\) \(4\) or squaring both sides we have \(b = 4\) same insuff
1) + 2)\(b = 4\) and from one \(a = b\)-----> \(4*4\) \(=\)\(16\) we have\(a * b\) suff
But the OA is different
2) \(b = 2\) ---> basically \(\sqrt{b}\) \(=\) \(4\) or squaring both sides we have \(b = 4\) same insuff
1) + 2)\(b = 4\) and from one \(a = b\)-----> \(4*4\) \(=\)\(16\) we have\(a * b\) suff
But the OA is different
15 Oct 2012, 07:47
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The answer is E. When you sum up statements 1 and 2, you only considered the case when a=b. You forget to consider the case a=-b. This would mean that a = 4 & a = -4; the the answer cannot be determined.
15 Oct 2012, 07:49
Kudos
Bookmarks
If bot a and b are nonzero integers, what is the value of a*b ?
(1) a^2=b^2 --> \(|a|=|b|\). If \(a=b=1\), then \(ab=1\) but if \(a=b=2\), then \(ab=4\). Not sufficient.
(2) \(\sqrt{b}=2\) --> \(b=4\). Nothing about \(a\). Not sufficient.
(1)+(2) Since from (2) \(b=4\), then from (1) \(a^2=16\), thus \(a=4\) or \(a=-4\) --> \(ab=4*4=16\) or \(ab=(-4)*4=-16\). Not sufficient.
Answer: E.
Hope it's clear.
(1) a^2=b^2 --> \(|a|=|b|\). If \(a=b=1\), then \(ab=1\) but if \(a=b=2\), then \(ab=4\). Not sufficient.
(2) \(\sqrt{b}=2\) --> \(b=4\). Nothing about \(a\). Not sufficient.
(1)+(2) Since from (2) \(b=4\), then from (1) \(a^2=16\), thus \(a=4\) or \(a=-4\) --> \(ab=4*4=16\) or \(ab=(-4)*4=-16\). Not sufficient.
Answer: E.
Hope it's clear.
