On 2008 Jan 17 , at 1:12 AM, Mike Millet wrote:
The first problem he put up on the board was one of those "if train
x travels at a 60 km/h over a distance of x kilometers and train y
travels a speed of 80 km/h over x kilometers, how long would it take
before they meet?" or something to that effect.
When he asked for questions on the problem, several hands shot up
with the invariable "what's a kilometer?".
The phrase "or something like that" must include some additional facts
or it is insoluble regardless of units, but that is irrelevant to a
point that I want to make.
In this type of problem (provided the missing information is given),
it makes absolutely no difference what distant unit is used, so long
as the same distance unit is used throughout*. The problem can be done
WITHOUT KNOWING what distance unit is used (except that all are the
same).
The sad thing is the fact that the students even thought it was
relevant to ask what the kilometre was.
Regards,
Bill Hooper
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*such as kilometres for distances and kilometres per hour for speeds,
or miles for distances and miles per hour for speeds,
or zilches for distance and zilches per hour for speeds,
etc.
(You get the picture.)
