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Thursday, December 20, 2007

This problem can't be done.

Right?

Not enough information

Or way too much information, as the case may be.


Two trains are loaded with equal amounts of rock salt and ball bearings. Train A leaves Frogboro at 10:00 A.M. carrying 62 passengers. Train B leaves Toadville at 11:30 A.M. carrying 104 passengers. If Train A is raveling at a speed of 5 mph and makes four stops, and Train B is traveling at an average speed of 86 mph and makes three stops, and the trains both arrive at Lizard Hollow at 4:30 P.M., what is the average weight of the passengers on Train B?

source:
Kaplan SSAT & ISEE 2007 edition
p. 155
at

4 comments:

  1. AnonymousDecember 20, 2007 at 4:02 PM

    It is a trick question. Trains traveling at an average speed of 86 MPH are not used for freight and thus would not be carrying rock salt and ball bearings.

    -Mark Roulo

    ReplyDelete
  2. Doug SundsethDecember 20, 2007 at 4:18 PM

    As Mark noted, bulk quantities of rock salt and ball bearings are carried by neither train. Thus, each train carries less than or equal to 18.6 slugs of ball bearings and 396.88 Newtons mass of rock salt.

    Since the gravitational attraction of the sun acts to counteract the gravitational attraction of the earth during the period discussed in the problem, the answer is 86 kg weight.

    This assumes, of course, the standard allowance for racks to keep the ball bearings from rolling around on the floor of the train and tripping the conductor.

    (There is no information in the problem that can be used to solve anything, as far as I can see.)

    ReplyDelete
  3. Catherine JohnsonDecember 20, 2007 at 5:37 PM

    I feel better now.

    ReplyDelete
  4. AnonymousDecember 20, 2007 at 10:55 PM

    "There is no information in the problem that can be used to solve anything, as far as I can see."

    HAH!!!!

    Not true ...

    This is a statistics problem in disguise!

    No, really. It is.

    It turns out that "Lizard Hollow" is a real place ... in Arizona. So this tells us that this taking place in the U.S.

    From this, we only need to know the average weight of a U.S. adult (we can assume very few children on a train ride like this between 11:30 and 4:30). Given an average weight and a standard deviation (plus an assumption about IID), we can provide a total weight with a +/- range to, say, 2 standard deviations.

    :-)

    -Mark R.

    ReplyDelete