Is x negative? (1) n*n*n(1-x*x) < 0 (2) x*x-1 < 0 The

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Is x negative? (1) n*n*n(1-x*x) < 0 (2) x*x-1 < 0 The [#permalink]

19 Sep 2003, 08:36

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1. Is x negative?

(1) n*n*n(1-x*x) < 0
(2) x*x-1 < 0

The answer is C.

2. What is the volume of a certain rectangular solid?

(1) Two adjacent faces of the solid have areas 15 and 24, respectively.
(2) Each of two opposite faces of the solid has area 40.

The answer is C.

Thanks:)[/code][/quote]

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Re: Please help me with two DS [#permalink]

19 Sep 2003, 08:58

Joviest wrote:

(1) n*n*n(1-x*x) < 0

Here (1-x^2) can be greater than or less than 0

So cant say

(2) x*x-1 < 0

x^2 -1 < 0

x^2 < 1

Gives x >-1 or x<1 again cant say yes or no

Combine, we now know from 2 that 1-x^2 > 0

So that means x^2 <1 which means x>-1 and x<1

The answer is C.

2. What is the volume of a certain rectangular solid?

(1) Two adjacent faces of the solid have areas 15 and 24, respectively.
(2) Each of two opposite faces of the solid has area 40.

The answer is C.

Thanks:)[/code]

[/quote]

Its a bit confusing the way you have written the powers ...

(1) n*n*n(1-x*x) < 0

Here (1-x^2) can be greater than or less than 0

So cant say

(2) x*x-1 < 0

x^2 -1 < 0

x^2 < 1

Gives x >-1 or x<1 again cant say yes or no..insufficient

Combine, we now know from 2 that 1-x^2 > 0

but that still doesnt give the answer

I think E

2. What is the volume of a certain rectangular solid?

(1) Two adjacent faces of the solid have areas 15 and 24, respectively.

you can take any set lb,bh,lh ..it will get you the same answer

b*h = 15
l*h = 24

not sufficient three unknowns ,two equations.

(2) Each of two opposite faces of the solid has area 40.

l*b = 40

Not sufficient

Combine , three unknowns, three equations, sufficient...C

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[#permalink]

19 Sep 2003, 14:47

I think the answer to the second question is C because...

If sides are adjacent, it means they share the length value of one side.
If sides are 15 and 24, the only common denominators are 3 and 1.

If the common leg is 3....
8 x 3 (24=area)
5 x 3 (15=area)
VOLUME = 8 x 3 x 5 = 120

if the common leg is 1...
24 x 1 (24=area)
15 x 1 (15=area)
VOLUME = 24 x 1 x 15= 360

A tells you it's either 120 or 360.

B tells you an area of a side is 40. That's impossible under the 2nd A scenario. The first A scenario fits right in.

you have side areas of
24 3x8
15 3x5
40 8x5

I'm not sure yet about #1

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[#permalink]

03 Nov 2003, 13:01

agree with praet on the first one..ans is E.
consider the value of x=-1/2 and x= 1/2.

in both cases x2 < 1.

[#permalink] 03 Nov 2003, 13:01

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Is x negative? (1) n*n*n(1-x*x) < 0 (2) x*x-1 < 0 The

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