This Week's NPR Weekend Edition Sunday Puzzle

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

Ash Wyllie wrote:
A private pilot has a four-seat plane, and he's offered to take three
friends up for a flight. To do his load and fuel calculations the pilot
needs to know the combined weight of his three passengers. Now, the
three passengers are sensitive about their weight, and none of them will
let anyone else know how much he weighs. And no scale at the flying club
is big enough to weigh more than one person at a time. How does the
pilot quickly get the accurate combined weight of the three passengers?


This one has beeen aroound before. 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.

I like that!
Simple and elegant.

This one has been around before

On Car Talk, about a year ago. The question was about the mechanics in the
Last Chance Garage wanting to know their *average* wages, so there was an
additional step. Dedicated NPR listeners should have no problem with this
one.

-- David Brooks

"Ash Wyllie" wrote in message
...
john smith opined

The Current Challenge (given February 22, 2004):

A private pilot has a four-seat plane, and he's offered to take three
friends up for a flight. To do his load and fuel calculations the pilot
needs to know the combined weight of his three passengers. Now, the
three passengers are sensitive about their weight, and none of them will
let anyone else know how much he weighs. And no scale at the flying club
is big enough to weigh more than one person at a time. How does the
pilot quickly get the accurate combined weight of the three passengers?

E-mail your answer to , or send a post card to:

PUZZLE
Weekend Edition Sunday
National Public Radio
635 Massachusetts Ave., NW
Washington, DC 20001


This one has beeen aroound before. 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.


-ash
Cthulhu for President!
Why vote for a lesser evil?