.NET Math Quiz

I have decided to test how numerate (mathematically literate) my readership is.  These are questions that one might find in a high school test... except I substituted the set of ints or longs for that of integers and the set of doubles for that of reals.

For each statement, answer true or false.

If x, y, z are ints, ...

1. If x < 0, then -x > 0.
2. If x = -x, then x = 0.
3. If x -y > 0, then x > y.
4. If x and y are positive , then x + y > x.
5. If x and y are positive, then (double)x * (double)y = (long)x * (long)y.
6. If x-y>0 and y-z>0, then x-z>0.

If x, y, z are doubles, ...

1. x = x.
2. If x>y is false, then x<=y is true.
3. If x > 0, then x - x = 0.
4. If x and y are positive integers, then x + y > x.
5. If x and y are positive integers, then the statement "x + y = x for all y" is false for all x.
6. If x <= 0 is false, then x > 0.
7. If x and y are longs, then (double)(x + y) = (long)(x + y).
8. if x.Equals(y), then x = y.
9. If x.Equals(-x), then x = 0.
10. if x.ComparesTo(y) < 0, then x < y.

Comments

[Brad Wilson]

Subtitled: Know Your Edge Cases

:)

[Chris Nahr]

Nice test, let's see...

int 1 and 2 are true.
int 3 and 6 should be true, unless there's some nasty trick that I don't grasp right now.
int 4 is false because of possible overflow.
int 5 is false because of possible overflow or rounding errors.

I'm not even going to touch the double section until you tell us that there can be no NaN or Inf values. :)

PS: SharpReader doesn't display any comments for your blog. No idea why that might be so.

[Jeroen Frijters]

Only the two 5s are true, all the others are false.

[Jeroen Frijters]

Uhhmm.. The int 5 is also false. I still think the double 5 is true though.

[James Curran]

int 5 is false as well. (Think: Digits)

[aminah]

If x>y, x-y >0, andd if x