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#1 2008-01-21 07:21:12
- tony123
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- Registered: 2007-08-03
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3/5
If
then(a) x<y ( B) x> y (C)x=y (D)noon of these
Last edited by tony123 (2008-01-21 07:21:59)
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#2 2008-01-21 08:04:56
- Daniel123
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Re: 3/5
(a) can be true; for example x can be 3 and y can be 5
(b) can also be true (but then (a) obviously wouldn't); for example, x can be -3 and y can be -5
(c) cannot be true
(d) cannot be true, as (a) or (b) can be true
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#3 2008-01-21 08:23:36
- mathsyperson
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Re: 3/5
I interpret (D) as "It is impossible to say that any previous statement is true", as opposed to "The previous statements are not true".
If it was the second case then you could immediately tell it was false without reading the question, because one of x<y, x=y and x>y will always be true, regardless of what x and y are.
The correct answer is (D) by that interpretation, because as Daniel has shown, it's possible for (A) or (B) to be true (and so we don't know which is).
Why did the vector cross the road?
It wanted to be normal.
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#4 2008-01-21 10:18:30
- MathsIsFun
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Re: 3/5
Yes, I would also say (D) because you cannot rely on (A) being true, neither can you rely on (B).
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
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#5 2008-01-21 10:43:11
- Daniel123
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Re: 3/5
I interpret (D) as "It is impossible to say that any previous statement is true", as opposed to "The previous statements are not true".
I would (now) also say (D). 
Last edited by Daniel123 (2008-01-21 10:43:26)
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#6 2008-01-23 01:51:10
- Jai Ganesh
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Re: 3/5
I too agree. (d) is the best option.
It has not been said whether a and b belong to set of natural numbers, integers or rational numbers.
It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.
Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.
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#7 2008-01-23 05:06:54
- mathsyperson
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Re: 3/5
Fair point, if we're dealing with naturals then the answer would be (A).
Tony's puzzles tend to work with reals though.
Why did the vector cross the road?
It wanted to be normal.
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