Quote:
Originally Posted by janvdl  Dist. = speed x time
For one train to complete the journey:   mins
But now we have 2 trains, going at the same speed, so they will meet at 50 miles. So for the trains to meet each other will take 100 mins.
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Now for the bird.
The bird has 100 minutes to go as far as he can before his imminent and brutal death... (Oh the calamity)    
EDIT: This looks like such a small distance. Something doesn't seem right.
EDIT2: Messed up with the time, let me correct it.
EDIT3: There we go, 100 miles  |
nice solution. another way to think about it:
two trains heading at each other at 30 mph each could be thought of as one train standing still and the other train heading toward it at 60 mph. the trains start at 100 miles apart. the bird flies off the train standing still and flies towards the train heading its way. the train and the bird meet halfway, that is, when each travel 50 miles, since they are moving at the same speed. once the bird touches the train and flies the other way, it does not pass the moving train, but stays exactly in front of it as it crashes into the standing train (since they are moving at the same speed). thus the bird flies 50 miles back to the standing train where it is crushed. thus the total distance the bird flies is 100 miles. this is a "logical solution," no knowledge of the formula for speed is necessary. it's pretty easy and quick to think through, so when you think for a few seconds and blurt out the answer, everyone can be impressed at your (apparent) calculating power. "How did he work that out so quickly?"
TPH, this question seems similar to one you've asked before. i think it was in another Problem of the Week thread.