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If ab=c, b=? [#permalink]
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19 Dec 2016, 01:10
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45% (00:59) correct 55% (01:04) wrong based on 161 sessions
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If ab=c, b=? 1) c≠0 2) ac≤0
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Re: If ab=c, b=? [#permalink]
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19 Dec 2016, 01:22
b=c/a ?? We need to find the value.
1) c not equals 0... Clearly Insufficient
2) ac<= 0. So I)ac<= 0 I.e a<=c if a=c;b=1, and if a<c we don't have any value 2) (ac) <= 0 I.e c<= a. Same as above So clearly insufficient.
Combining the 2 we don't get any concrete answer so answer is (E)
Correct me if wrong
Omkar Kamat When The Going Gets Tough, The Tough Gets Going !!



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Re: If ab=c, b=? [#permalink]
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20 Dec 2016, 08:13
what's wrong with option E please explain



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Re: If ab=c, b=? [#permalink]
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20 Dec 2016, 09:49
Omkar.kamat wrote: b=c/a ?? We need to find the value.
1) c not equals 0... Clearly Insufficient
2) ac<= 0. So I)ac<= 0 I.e a<=c if a=c;b=1, and if a<c we don't have any value 2) (ac) <= 0 I.e c<= a. Same as above So clearly insufficient.
Combining the 2 we don't get any concrete answer so answer is (E)
Correct me if wrong
Omkar Kamat When The Going Gets Tough, The Tough Gets Going !! 2nd stmnt can't be less than zero but it can be equal to zero. therefore a=c. abc=0; a=c; c(b1)=0. from stmnt 1 C not equal to zero . b=1. solution is C



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Re: If ab=c, b=? [#permalink]
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20 Dec 2016, 11:08
Initially i was thinking around c but still took E :/, anyway thank you robu Sent from my HM 1SW using GMAT Club Forum mobile app



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Re: If ab=c, b=? [#permalink]
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21 Dec 2016, 01:42
==> In the original condition, there are 3 variables (a, b, c) and 1 equation (ab=c). In order to match the number of variables to the number of equations, there must be 2 equations, and therefore C is most likely to be the answer. By solving con 1) and con 2), from con 2), you get a=c, and if you substitute this into ab=x, you get ab=a. In order to divide a from both sides, it needs to be a≠0. From con 1), it is c=a≠0, and if you divide both sides by a, you get b=1, hence it is unique and sufficient. Therefore, the answer is C. Answer: C
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Re: If ab=c, b=? [#permalink]
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24 Dec 2016, 01:57
Omkar.kamat wrote: b=c/a ?? We need to find the value.
1) c not equals 0... Clearly Insufficient
2) ac<= 0. So I)ac<= 0 I.e a<=c if a=c;b=1, and if a<c we don't have any value 2) (ac) <= 0 I.e c<= a. Same as above So clearly insufficient.
Combining the 2 we don't get any concrete answer so answer is (E)
Correct me if wrong
Omkar Kamat When The Going Gets Tough, The Tough Gets Going !! ac can never be <0 it can only equate to ac=0 => a=c from statement 1 A not equals C therefore b=c/a =1



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Re: If ab=c, b=? [#permalink]
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24 Dec 2016, 02:17
robu wrote: Omkar.kamat wrote: b=c/a ?? We need to find the value.
1) c not equals 0... Clearly Insufficient
2) ac<= 0. So I)ac<= 0 I.e a<=c if a=c;b=1, and if a<c we don't have any value 2) (ac) <= 0 I.e c<= a. Same as above So clearly insufficient.
Combining the 2 we don't get any concrete answer so answer is (E)
Correct me if wrong
Omkar Kamat When The Going Gets Tough, The Tough Gets Going !! 2nd stmnt can't be less than zero but it can be equal to zero. therefore a=c. abc=0; a=c; c(b1)=0. from stmnt 1 C not equal to zero . b=1. solution is C Thanks Robu , I completely missed out that modulus of something cannot be < 0 Omkar Kamat When The Going Gets Tough, The Tough Gets Going !!



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If ab=c, b=? [#permalink]
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10 Jan 2017, 23:17
nks2611 wrote: what's wrong with option E please explain Hi nks2611, In the original condition, there are 3 variables(a,b,c) and 1 equation(ab=c). Hence, C is likely to be an answer. Happy Studying! Math Revolution
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Re: If ab=c, b=? [#permalink]
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04 May 2017, 16:05
how can ac<=0? ac is already >0. only option left is if ac = 0 ac=0 > a=c a+c=0 c=a same thing if ab=c and a=c, then b=1.
my vision was poor, and i thought 1st statement says c=0...



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Re: If ab=c, b=? [#permalink]
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04 May 2017, 22:40
mvictor wrote: how can ac<=0? ac is already >0. only option left is if ac = 0 ac=0 > a=c a+c=0 c=a same thing if ab=c and a=c, then b=1.
my vision was poor, and i thought 1st statement says c=0... Since \(ac \ge 0\), \(ac \le 0\) means \(a  c = 0\) or \(a = c\). When we consider both conditions together, \(ab = c\) is equivalent to \(ab  c = 0\) or \(ab  c = cb  c = c ( b  1 ) = 0\). Since \(c \ne 0\), we have \(b = 1\). Therefore the answer is C.
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Re: If ab=c, b=? [#permalink]
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05 May 2017, 06:25
MathRevolution wrote: mvictor wrote: how can ac<=0? ac is already >0. only option left is if ac = 0 ac=0 > a=c a+c=0 c=a same thing if ab=c and a=c, then b=1.
my vision was poor, and i thought 1st statement says c=0... Since \(ac \ge 0\), \(ac \le 0\) means \(a  c = 0\) or \(a = c\). When we consider both conditions together, \(ab = c\) is equivalent to \(ab  c = 0\) or \(ab  c = cb  c = c ( b  1 ) = 0\). Since \(c \ne 0\), we have \(b = 1\). Therefore the answer is C. thanks! this actually makes sense! I didn't think of that!










