This Week's NPR Weekend Edition Sunday Puzzle

What you do is whisper a random number to
person 1. He adds his weight to that number and whispers the result to person
2. He and person 3 dothe same. Person 3 tells the pilot the result of his
calculation. The pilot then subtracts the original random number and comes out
with the total of the passenger's weights.


This works as long as all passengers are good at math, and there are no
telephone errors.

The likelyhood of this is not something I want to contemplate.

Jose

--
(for Email, make the obvious changes in my address)

Teacherjh wrote:


What you do is whisper a random number to
person 1. He adds his weight to that number and whispers the result to person
2. He and person 3 dothe same. Person 3 tells the pilot the result of his
calculation. The pilot then subtracts the original random number and comes out
with the total of the passenger's weights.


This works as long as all passengers are good at math, and there are no
telephone errors.

Ok, then punch some random number into your calculator and have each passenger
add in his/her weight on that.

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

Ok, then punch some random number into your calculator and have each passenger
add in his/her weight on that.


....and do it two or three times with different numbers to assure yourself that
nobody ELSE made errors. I've watched too many people do math and science,
with and without calculators, to trust such results. In calculating the speed
of a baseball (starting with reasonable assumptions) I've seen a lot of
students put down "0.024121331 mph" because that's what the calculator said.

If there's a W&B to be done, it will be ME that does it. I mever nake
mistakes.

Jose

--
(for Email, make the obvious changes in my address)

"Teacherjh" wrote in message
...
If there's a W&B to be done, it will be ME that does it. I mever nake
mistakes.

Ne either. Oh, I think I found your "n". Want to trade?

The funny thing about this whole problem is that it ignores the fact that
you need not the combined weights for all three passengers, but the combined
weights of two of them (sitting in the rear seat) and the weight of the
front passenger (added to your own, of course).

It's a nice "brain teaser", but it has no practical application, at least
not with the solutions given so far.

One theoretically accurate solution would be to load up the airplane, then
measure the area of the contact patches of each tire. By dividing the area
by the tire pressure (making sure the units match, of course...for example,
measuring area in square inches, and pressure in psi), you get the
distribution of the weight at each tire, which gives you not only total
aircraft weight, but also enough information to calculate a moment, to which
you can include your own weight and position (since I'm assuming the pilot
is not in the plane, but rather is the one taking measurements), and
determine the exact location of the CG.

Of course, there's no really practical way to measure the area of the
contact patch, what with it not being exactly rectangular, there being voids
where the tread has gaps, and the like. But unlike the "add 'em all up"
solution, at least this one has the potential to actually give useful
information, if only the impracticalities could be addressed.

Pete