Is ab

Question

Is ab < 0 ?

(1) a = b - 6
(2) b < 0

Kudos for a correct  solution .

AmoyV · Answer

1. Not Sufficient. If b>6, a>0 and ab>0 If b=6, then ab=0 If 00 2. Not Sufficient No information about a given. 1 and 2. Sufficient. Combining, we know that only the last scenario discussed in statement 1 holds. Hence the answer to the question is "No". ab is not < 0 Answer: C

CounterSniper · Answer

statement 1 tells us that a can be + or -ve and nothing significant in itself to concur ab < 0, so it is insufficient.
Statement 2 tells us that b < 0 insufficient to conclude whether ab < 0

combining both 
we get a < b or a is -ve

so ab = some number which is +ve and hence ab > 0 thus

we get the answer combining both so (C)

musunna · Answer

For simplicity, assuming ab>0 and it's only possible if either a<0 or b<0.

Statement 1 says a = b - 6. Here nothing is said about b. thus NOT sufficient.
Statement 1 says b < 0. But no information about a.
If a <0, then ab>0 and if a> 0, then ab<0. multiple answers. thus statement (2) alone is NOT sufficient.

Combining 1 & 2, we get b<0 and a = [neg value]-6 i.e. a <0.
Here we get a single answer : ab>0
So, option (c) wins.

keats · Answer

Is ab < 0 ?

(1) a = b - 6
(2) b < 0

___________________________________

The question asks if a and b are opposite signs.
ST 1: a = b - 6
b = 7 a = 1 No
b = 4 a = -2 Yes
This statement is not sufficient

ST 2: b<0
a can be less than or greater than zero. Again, not sufficient.

ST 1 + 2 
b is negative 
and a =b - 6
If b is negative, a will always be negative.
This means that ab will be positive. A definite NO.

Therefore, C is sufficient

Vinayprajapati · Answer

Can be represented on number line: STATEMENT1: ------------a---------(a is 6 less thn b)--------b------------ Alone NS STATEMENT2: b<0 Alone NS Combining 1 & 2 b<0 => a<0 =>ab>0 Therefore 'C'

daschirodeep · Answer

Statement I : a= b- 6 if, b<0, then a<0 . ab becomes > 0 . Answer to the question : NO if, b=0 , then a=6. ab becomes 0. Answer to the question : NO if, 0 0, Answer to the question : NO if, a>0, ab becomes < 0, Answer to the question : YES No unique answer. NOT SUFFICIENT. Both Statement I & II, As, b<0 and a is 6 less than b So, a<0 ab<0. Answer to the question : YES Only one unique answer. SUFFICIENT.

MathRevolution · Answer

There are 2 variables (a and b) in the original condition. In order to match the number of variables and the number of equations, we need 2 equations. Since the condition 1) and the condition 2) each has 1 equation, there is high chance that C is the correct answer. Using both the condition 1) and the condition 2), we get a=b-6<0 and b<0. Since ab>0, the answer is no and the conditions are not sufficient. Thus, the correct answer is C.

l For cases where we need 2 more equations, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.

bumpbot · Answer

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Is ab < 0 ? (1) a = b - 6 (2) b < 0

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