3 ms·
> 3. They approach one another at 30000 mph = 500 miles per minute, so two minutes before they collide they are 1000 miles apart, and who cares that they start
by JshWright 12y ago
> 3. They approach one another at 30000 mph = 500 miles per minute, so two minutes before they collide they are 1000 miles apart, and who cares that they start out 1317 miles apart?
It was clearly just a distraction, and apparently an effective one, as the question was "calculate how far apart they are _one_ minute before they collide".
- LanceH 12y agoThe version I heard that truly leads a calculus student down the wrong path is along the lines of: Train a is going 40 mph, train b 60 mph. They are 200 miles apart on the same track, headed directly for each other. There is a bird flying between the two at 100 mph, starting from train a. Each time he reaches a train he turns around and heads back to the other train. How far does the bird travel before he is crushed between the trains?
- anon4 12y agoI don't see what's so hard about that one, it's a simple infinite sum.
- jameshart 12y agoThere's an easier way than an infinite sum.
- Khao 12y ago40mph + 60mph = 100mph, so they will travel for 2 hours before they hit each other. The bird flying at 100 mph for 2 hours will travel 200 miles.
- thesteamboat 12y agoanon4 is referencing one of the tellings of this story where famous scientist [usually Von Neumann] is given this problem as a brainteaser and responds instantly having done it the `hard way'. http://mathforum.org/dr.math/faq/faq.fly.trains.html http://mathforum.org/dr.math/faq/faq.fly.trains.html