Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**tony123****Member**- Registered: 2007-08-03
- Posts: 192

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)*

Offline

**Daniel123****Member**- Registered: 2007-05-23
- Posts: 663

(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

Offline

**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

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.

Offline

**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,685

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

Offline

**Daniel123****Member**- Registered: 2007-05-23
- Posts: 663

mathsyperson wrote:

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)*

Offline

**ganesh****Administrator**- Registered: 2005-06-28
- Posts: 25,049

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 is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

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.

Offline