Inequalities

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Inequalities

by satyavegi » Sun Aug 12, 2012 10:01 pm
If a and b are integers, and |a| > |b|, is a · |b| < a - b?

(1) a < 0

(2) ab >= 0

OA E

Can someone explain this in detail ..i couldnt understand the explanation given in MGMAT
Source: — Data Sufficiency |

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by Anurag@Gurome » Sun Aug 12, 2012 10:07 pm
satyavegi wrote:If a and b are integers, and |a| > |b|, is a · |b| < a - b?

(1) a < 0

(2) ab >= 0

OA E

Can someone explain this in detail ..i couldnt understand the explanation given in MGMAT
(1) a < 0
If a = -3 and b = -1, then a * |b| = (-3) * 1 = -3, a - b = -3 + 1 = -2. Here, a * |b| < a - b.
If a = -3 and b = 0, then a * |b| = (-3) * 0 = 0, a - b = -3. Here, a * |b| > a - b.
No definite answer; NOT sufficient.

(2) ab ≥ 0
We can take the same examples as in statement 1:
If a = -3 and b = -1, then a * |b| = (-3) * 1 = -3, a - b = -3 + 1 = -2. Here, a * |b| < a - b.
If a = -3 and b = 0, then a * |b| = (-3) * 0 = 0, a - b = -3. Here, a * |b| > a - b.
No definite answer; NOT sufficient.

Combining (1) and (2), again we can take the same examples as above, there is no additional info; NOT sufficient.

The correct answer is E.
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by mcdesty » Tue Aug 14, 2012 9:44 pm
[a]> a.> a- b ..Rephrase

Is a.-a+b>0

is a( - 1) + b >0?

1) a<0 nothing about B just move on (a could be -3 and b 0(Yes) or a could be -3 and B 2 (No))No good

2) ab>=0
Both can be positive or negative ( a -3 and b -2 (No) a 3 and b 2(Yes)} No good

1 & 2) Both can only be negative or b = 0 (a -3 and b -2 (No) a -3 b 0 (Yes)

E