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If a>b, is a>c? 1) a/b > c/b 2) 5ab > 6bc

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If a>b, is a>c? 1) a/b > c/b 2) 5ab > 6bc [#permalink] New post   Updated on: 25 May 2016, 07:47
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59% (02:26) correct 41% (01:23) wrong based on 67 sessions
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If a>b, is a>c?

1) a/b > c/b
2) 5ab > 6bc

For each piece of additional information, I have used a plug-in numbers approach to provide affirmative and negative answers to the question. However, it took me more time than desired.

Could someone please explain to me an approach that can help me to solve this question in a quicker way?

Thank you so much.
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E

Originally posted by EBITDA on 25 May 2016, 03:56.
Last edited by Bunuel on 25 May 2016, 07:47, edited 1 time in total.
Moved to DS forum.
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chetan2u
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Re: If a>b, is a>c? 1) a/b > c/b 2) 5ab > 6bc [#permalink] New post   25 May 2016, 07:19
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EBITDA wrote:
If a>b, is a>c?

1) a/b > c/b
2) 5ab > 6bc

For each piece of additional information, I have used a plug-in numbers approach to provide affirmative and negative answers to the question. However, it took me more time than desired.

Could someone please explain to me an approach that can help me to solve this question in a quicker way?

Thank you so much.


You don't require to get into the plugging in...
solve the equations..

1) a/b > c/b
\(\frac{a}{b}-\frac{c}{b}>0................\frac{a-c}{b}>0\).............
a) if \(b>0, a-c>0... or... a>c...\)
b) If \(b<0,a-c<0... or... a<c...\)
so the answer depends on whether b is positive or negative..
Insuff

2) 5ab > 6bc
\(5ab-6bc>0..............b(5a-6c)>0...\)
again two cases..
a) if \(b>0, 5a-6c>0... or.... 5a>6c...\)
b) If \(b<0, 5a-6c<0.... or... 5a<6c...\)
so the answer depends on whether b is positive or negative..
Insuff

combined..
still the cases remain same and depend on whether b<0 and b>0..
Insuff

E
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Re: If a>b, is a>c? 1) a/b > c/b 2) 5ab > 6bc [#permalink] New post   25 May 2016, 07:46
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EBITDA wrote:
If a>b, is a>c?

1) a/b > c/b
2) 5ab > 6bc

For each piece of additional information, I have used a plug-in numbers approach to provide affirmative and negative answers to the question. However, it took me more time than desired.

Could someone please explain to me an approach that can help me to solve this question in a quicker way?

Thank you so much.


Please post DS questions in DS forum. Thank you.
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Re: If a>b, is a>c? 1) a/b > c/b 2) 5ab > 6bc [#permalink] New post   25 May 2016, 08:35
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EBITDA wrote:
If a>b, is a>c?

1) a/b > c/b
2) 5ab > 6bc

For each piece of additional information, I have used a plug-in numbers approach to provide affirmative and negative answers to the question. However, it took me more time than desired.

Could someone please explain to me an approach that can help me to solve this question in a quicker way?

Thank you so much.


i plugged no number in this question. relation between a and b is given and asked between a and c.

statement-1 says a/b > c/b. it would depend on the sign of b whether a>c or not. here is why:
a/b - b/c > 0
(1/b)*(a-c) > 0
it means either a-c and b both are positive or both are negative.
insufficient.

statement-2 does not give any clue about the sign of a, b or c. insuff.

if we combine stmt-1 and stmt-2, we are left with no information about signs of a,b,c.
hence answer should be E.
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Re: If a>b, is a>c? 1) a/b > c/b 2) 5ab > 6bc [#permalink] New post   18 Oct 2016, 07:59
EBITDA wrote:
If a>b, is a>c?

1) a/b > c/b
2) 5ab > 6bc
Thank you so much.


I spent slightly more than 2 minutes on this question...
the trick here is to consider all possible values, including negative and fractions.

1.
suppose a=-2, b=-3
a/b = 2/3
suppose c=1 and b=-3
c/b = -1/3
but c>a

test with positive numbers...and get vice versa.

A and D are eliminated.

2. 5ab > 6bc
suppose a=2, b=1, and c=1.
a>c.

suppose a=-1, b=-2, c=1
5ab > 6bc
but a<c
not sufficient.

B is out.

1+2
we can have a>c or c<a if we consider negative numbers as well.

D is out, and the answer should be E.
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Re: If a>b, is a>c? 1) a/b > c/b 2) 5ab > 6bc [#permalink]
18 Oct 2016, 07:59
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Bunuel
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