Latest Elitmus Aptitude Question SOLUTION: is (a*b) positive? a) (a+b)^2 < (a-b)^2 b) (a+b)^3 < (a-b)^3

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(#M40038394) ELITMUS Numerical Ability question data sufficiency 17-aug-14 Keep an EYE

is (a*b) positive?
a) (a+b)^2 < (a-b)^2
b) (a+b)^3 < (a-b)^3

Asked In Elitmus ankita soni (9 years ago)

Unsolved Read Solution (9)

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Read Solution (9) :

RAKESH  (9 years ago)

only (a) is sufficient alone but cannot be answered with the help of other

a) (a+b)^2 < (a-b)^2
=> (a+b)^2 - (a-b)^2 < 0
=> a*b < 0

b) (a+b)^3 < (a-b)^3
=> 2b*(3a^2+b^2) < 0
=> b < 0
we can't tell about a*b without knowing about a .

Is this solution Helpfull? Yes (26) | No (3)  

Devraj Dad  (9 years ago)

either of the 1 statement is required

Is this solution Helpfull? Yes (2) | No (1)  

arjun kumar jha  (9 years ago)

from statement a it is clear that...a*b is negative....and from 2 we can conclude that.a*b may be positive so either of the statement can lead to the result

Is this solution Helpfull? Yes (1) | No   

Minakshi Kumari  (9 years ago)

Yes,(a+b)^2-(a-b)^20; Hence ab>0 mean a*b is positive .same apply fir b option.

Is this solution Helpfull? Yes (1) | No (3)  

sunil kumar  (9 years ago)

a or b anyone one of them can be negative but not both in first case so
a) a*b is negative

a and b both can be negative and only b can be negative
b) a*b is positive or a*b is negative

Is this solution Helpfull? Yes (1) | No (1)  

siddharth prakash singh  (9 years ago)

since (a+b)^2 - (a-b)^2= 4ab
from option a) (a+b)^2 - (a-b)^2 < 0
so 4ab < 0
=> ab < 0
from option b) (a+b)^3 - (a-b)^3 b < 0 ; but we cant comment about the value of a. a can be either positive or negative. so correspondingly ab can be negative or positive.

so only option (a) is sufficient to answer alone but cannot be answered with the help of other

Is this solution Helpfull? Yes (1) | No   

Ravichandran Ashwin  (9 years ago)

Only option (a) can be sufficient to find a*b as we can determine if a^2+b^2+2*a*b a^3+b^3+3*a*b(a+b) we cannot knoow a*b as we don't have values of a and b each from equation.So second option cannot be used to determne a*b

Is this solution Helpfull? Yes | No   

tushar varshney  (9 years ago)

only option a is sufficient.and b is not sufficient

Is this solution Helpfull? Yes | No   

M.Prasanth  (9 years ago)

mr rakesh,for a) a*b

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