OpenEuphoria

Re: A Teaser Solving Program

• Posted by Jason Gade <jaygade at yahoo.??m> Oct 08, 2007
• 591 views

Tristen Wilson wrote:
> 
> > What is it that you would want the program to do?  Point out the flaw in 
> > the text?  This is an old "brain teaser" that uses a false statement to
> > confuse the listener.
> > 
> > Assuming that you're really asking what the answer is, then it's that they
> > didn't pay $27.  They paid $25 for the room, and the clerk "split" the 
> > change with them.  The hotel got $25, the clerk got $2, and they kept the
> > other $3.
> > 
> > Matt
> I'm severely confused!

I've been trying to figure out how to explain this problem. The error is pretty
subtle and I had to look it up. I've seen the problem before but I had forgotten.

This is my third attempt to explain it (I canceled the others).

The room cost $25. The students paid $30. They were refunded $5. Of that $5, $2
went to the clerk.

So the students paid $27 for the room. Of that $27, $25 went to the hotel and $2
went to the clerk. The $3 is a red herring and the extra $1 is a phantom.

I don't know how to solve a basic mathematical error with a computer.

$25 + $5 = $30 -- room charge plus overpayment equals total.
$25 + $2 = $27 -- refund $3 to the students (subtract $3 from both sides)
$25 = $25 -- give the clerk his $2 cut (subtract $2 from both sides)

Less confused? Me neither. But that's why it's a puzzle. Basically the reverse
of the problem is wrong -- the $2 shouldn't be added, it should be subtracted.

$30 total - $3 to students - $2 to clerk = room cost ($25) whereas the problem
says $30 total - $3 to students + $2 to clerk = room cost ($25). See the problem?

--
A complex system that works is invariably found to have evolved from a simple
system that works.
--John Gall's 15th law of Systemantics.

"Premature optimization is the root of all evil in programming."
--C.A.R. Hoare

j.