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Source: — Data Sufficiency |
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by mehravikas » Sun Oct 04, 2009 3:14 pm
IMO - A

Given that x is -ve
1. x^2 > 9 - therefore x will be less than -3
2. x^3 < -9 - therefore x < -2.3 (guessed on this value because cube root of 8 is 2 so cube root of 9 must be greater than 2).

x < -2.3 but its not sure that x will be less than -3
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by heshamelaziry » Sun Oct 04, 2009 4:06 pm
mehravikas wrote:IMO - A

Given that x is -ve
1. x^2 > 9 - therefore x will be less than -3
2. x^3 < -9 - therefore x < -2.3 (guessed on this value because cube root of 8 is 2 so cube root of 9 must be greater than 2).

x < -2.3 but its not sure that x will be less than -3
I don't understand why 2 is insufficient, x < -3 or x > 3, and since x is -ve, it should be sufficient ???
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by mehravikas » Sun Oct 04, 2009 4:14 pm
How can you say that x < -3 in statement 2. What will be the cube root of 9 it will certainly be > 2

but the statement says x^3 < -9, therefore x < -2.3 (this is not an exact cube root)

If x < -2.3 then x could be the following:

1. x < -2.5
2. x < -2.9
3. x < -3

We cannot deduce the value of x.
heshamelaziry wrote:
mehravikas wrote:IMO - A

Given that x is -ve
1. x^2 > 9 - therefore x will be less than -3
2. x^3 < -9 - therefore x < -2.3 (guessed on this value because cube root of 8 is 2 so cube root of 9 must be greater than 2).

x < -2.3 but its not sure that x will be less than -3
I don't understand why 2 is insufficient, x < -3 or x > 3, and since x is -ve, it should be sufficient ???
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