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Fractions odd or even - Kaplan

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Fractions odd or even - Kaplan

by venmic » Sat Aug 07, 2010 8:30 am
is X odd

a) 2x-1 is odd

b) X^3 is odd ..

fractions are not odd or even so how can the answer by even or odd

This is a kaplan question

This question can be applied only to integers so if it is an integer then the answer should be D but the answer here is E
how is that possible
even and odd concept can never be applied to fraction

Will be nice if I can get a good explaination on this
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by selango » Sat Aug 07, 2010 8:52 am
x is odd?

stmt1,

2x-1 is odd

x=1,2x-1 is odd,x is odd

x=2,2x-1 is odd,x is even

Insuff

stmt2,

x^3 is odd-->x is odd

Odd*Odd*Odd=Odd.

x can be odd integer or cube root of an odd integer

InSuff

Combining 1 and 2,

If x is an integer only,2x-1 can be odd.

x is an integer-->x^3 is odd

-->x is odd

suff

Pick C
Last edited by selango on Sat Aug 07, 2010 9:59 am, edited 1 time in total.
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by arora007 » Sat Aug 07, 2010 9:16 am
The answer should be E.

for case 2

consider a real number [3^(1/3) ] , it cube is going to be 3, but the number itself is not ODD.

consider a number 27 its cube is odd, the number itself is also odd...

thus choice is insufficient.
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by venmic » Sat Aug 07, 2010 9:48 am
consider a real number [3^(1/3) ] , it cube is going to be 3, but the number itself is not ODD.

you mean --> cube root of 3 right ???

are we saying that is not odd
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by selango » Sat Aug 07, 2010 9:59 am
arora,

Edited my post..Do u agree with the solution..
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by arora007 » Sat Aug 07, 2010 11:18 am
venmic wrote:consider a real number [3^(1/3) ] , it cube is going to be 3, but the number itself is not ODD.

you mean --> cube root of 3 right ???

are we saying that is not odd
yes cube root of 3
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by arora007 » Sat Aug 07, 2010 11:22 am
selango wrote:x is odd?

stmt1,

2x-1 is odd

x=1,2x-1 is odd,x is odd

x=2,2x-1 is odd,x is even

Insuff

stmt2,

x^3 is odd-->x is odd

Odd*Odd*Odd=Odd.

x can be odd integer or cube root of an odd integer

InSuff

Combining 1 and 2,

If x is an integer only,2x-1 can be odd.

x is an integer-->x^3 is odd

-->x is odd

suff

Pick C
I am just wondering if i can select x=Zero
which would mean that 2x -1 would be -1
and wont fit in choice 2.....
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by selango » Sat Aug 07, 2010 11:34 am
We cannot choose x=0 as value of x must satisfy both equations..
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by arora007 » Sat Aug 07, 2010 11:45 am
selango wrote:We cannot choose x=0 as value of x must satisfy both equations..
you are right... it should be C...
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by kvcpk » Sat Aug 07, 2010 12:16 pm
venmic wrote:is X odd

a) 2x-1 is odd

b) X^3 is odd ..
a) 2x-1 is odd
let x= 1 is odd
2x-1 = 1 is odd
Let x = 2 is even
2x-1 = 3 is odd
INSUFF

b) x^3 is odd
Let x=3..ODD
x^3 = 27..ODD
Let x = 3^1/3.. NOT ODD
X = 3..ODD
INSUFF

Combining:
2X-1 is odd and x^3 is odd
2x -1 = 2p+1 where P is integer
x = P+1 -> Implies integer+1
Hence X is integer.
If integer^3 is odd, Integer should be odd.
hence C
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