| Title: | Mathematics at DEC |
| Moderator: | RUSURE::EDP |
| Created: | Mon Feb 03 1986 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2083 |
| Total number of notes: | 14613 |
I like math problems that attract the attention of people that basically "don't like math". For instance, puzzles without too many numbers in them, or that SEEM like perhaps they demand algebra, or even paper, but actually end up being fairly simple once reflected upon for a bit. Sometimes when first heard, the following seems not to have ENOUGH numbers in it ! A hiker has ventured part way across a narrow railroad bridge, when he hears a train approaching the bridge from behind him at 60 miles per hour ! He quickly realizes that at his current speed of hiking, he may retreat to the beginning of the bridge, or proceed to the end, with either strategy allowing him to reach the respective ends of the bridge just as the train does, and thus narrowly avoiding disaster. How fast is he hiking ? Who can supply the nicest graphics rendition of this problem for DEC terminals ? /Eric
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 316.1 | HARE::GILBERT | Tue Jul 16 1985 16:54 | 14 | ||
If the bridge is 12 miles long, and that the hiker is 1/3 of the way across it,
and he travels at 20 mph, he can reach one end in 12 minutes, or the other in
24 minutes. The difference in these times is the same as the train's transit
time, 12 minutes.
If he's 1/4 of the way across, and he travels at 30 mph, he can reach one end
in 6 minutes, or the other in 18 minutes. Again, the difference is the same as
the train's transit time, so this, too, is a possible solution to the problem.
"I knew a scout by the name of Jack,
Who took a hike on a railroad track.
The 8:15 came 'round the bend --
What kind of flowers you gonna send?"
| |||||
| 316.2 | SCOTTY::CCANTOR | Tue Jul 16 1985 18:36 | 12 | ||
h = s(1-2f), where: h = hiking speed s = train speed f = fraction of bridge the hiker has crossed Since the answer is far from unique, I don't see that you have supplied ENOUGH numbers. -cjc | |||||
| 316.3 | SPRITE::OSMAN | Tue Jul 16 1985 20:13 | 12 | ||
Gee, it sure is a bit embarrassing in here. Now that you've pointed it out (it's been several years since I heard the original problem), I guess there IS another number. It was stated in the original problem that: The hiker is a third of the way across the bridge when he hears the train. Sorry about the inaccuracy ! /Eric | |||||
| 316.4 | EIFFEL::BRETT | Tue Jul 16 1985 21:05 | 3 | ||
Wow! 20 mph! That hiker sure can travel - most only do 2.5 to 3! /Bevin | |||||
| 316.5 | SPRITE::OSMAN | Thu Jul 18 1985 18:03 | 3 | ||
Imagine being in that predicament (i.e. real narrow bridge, not room for both of you). You might compete with that speed too ! | |||||