IBM Research | Ponder This | August 2004 challenges

# Ponder This

## August 2004

<<July August September>>

Ponder This Challenge:

Puzzle for August 2004.

This month's puzzle comes from Joe Fendel, who writes:

Here's a puzzle I remember coming up with in high school. It was inspired by a request made one day that I come home immediately to do my chores, whereupon I would start walking home at a constant pace (I wasn't one to disobey), but I would try to find the longest possible route home (so as to put off doing my chores). Of course, I couldn't really walk in the opposite direction and claim to be "walking home." So I thought of the following problem:

Part 1:
Points A and B are on a plane surface, 1 mile apart. Suppose you must walk in a path consisting of N straight lines from point A to point B, such that at all times your (Euclidean) distance to point B is decreasing. What is the longest possible route length (as a function of N)?

Part 2:
Suppose the house is due north of the starting point, and on the way home, I always turn left (by less than 180 degrees). I still take a longest path according to the rules of Part 1. On the last leg of this longest path, I'm walking both northward and eastward (mostly eastward). What's the smallest possible value of N?

And of course your puzzlemaster has to add a "Part 3":
Suppose that in the setup of part 1, we have N=3; point A is 1 mile due east of point B; and the path is subject to the additional constraint that the last (third) line must be directed due south. Now what is the longest possible route?

Correct answers to all parts must be given.

We will post the names of those who submit a correct, original solution! If you don't want your name posted then please include such a statement in your submission!

We invite visitors to our website to submit an elegant solution. Send your submission to the webmaster.

If you have any problems you think we might enjoy, please send them in. All replies should be sent to: webmster@us.ibm.com

Challenge: 08/01/2004 @ 9:00 AM ET
Solution: 09/01/2004 @ 8:30 AM ET
List Updated: 08/01/2004 @ 9:00 AM ET

### People who answered correctly:

Tomas G. Rokicki (8.02.2004 @02:38:26 PM EDT)
Patrick J. LoPresti (8.02.2004 @03:20:00 PM EDT)
Colin Bell (8.02.2004 @07:44:32 PM EDT)
Alex Naverniouk and Igor Naverniouk (8.03.2004 @01:40:20 AM EDT)
Abhiman Chatra (8.03.2004 @04:29:00 AM EDT)
Vincent Vermaut (8.03.2004 @10:29:00 AM EDT)
Gaurav Agarwal (8.03.2004 @10:37:27 AM EDT)
Jose H. Nieto (8.03.2004 @10:39:00 AM EDT)
Hagen von Eitzen (8.03.2004 @12:05:51 PM EDT)
Dan Dima (8.03.2004 @12:53:05 PM EDT)
Kalyana Chakravarthy (8.03.2004 @01:31:00 PM EDT)
Joseph DeVincentis (8.04.2004 @12:08:24 AM EDT)
Hao Wu (8.04.2004 @12:30:55 AM EDT)
Li Jian (8.04.2004 @06:23:14 AM EDT)
Kevin Kenny (8.04.2004 @09:13:31 AM EDT)
Chris Hills (8.04.2004 @09:35:00 AM EDT)
Zaiyong Yang (8.04.2004 @11:30:00 AM EDT)
Jonathan Derryberry (8.04.2004 @12:59:03 PM EDT)
Karl D. Souz (8.04.2004 @02:41:31 PM EDT)
Prakash Chandra (8.04.2004 @03:17:34 PM EDT)
Gyozo Nagy (8.04.2004 @05:08:24 PM EDT)
Jayavel Sounderpandian (8.05.2004 @06:51:48 AM EDT)
aman_cc (8.05.2004 @12:25:13 PM EDT)
Vince Lynch (8.05.2004 @01:23:00 PM EDT)
Narayanan Rajamani (8.05.2004 @10:53:43 PM EDT)
Alan O'Donnell (8.06.2004 @06:39:00 AM EDT)
J. Lewandowski (8.06.2004 @11:57:24 AM EDT)
Chris Shannon (8.06.2004 @02:56:00 PM EDT)
Sedong Kwonyeon Kimyu (8.07.2004 @11:20:12 AM EDT)
Dr. John G. Fletcher (8.08.2004 @06:51:59 PM EDT)
Mayank M Kabra (8.09.2004 @02:57:22 AM EDT)
David McQuillan (8.09.2004 @05:21:30 PM EDT)
Guler Amos (8.10.2004 @10:01:24 AM EDT)
Ari (8.10.2004 @10:29:00 AM EDT)
Siva Dirisala (8.10.2004 @03:16:28 PM EDT)
Don Rice (8.10.2004 @06:00:00 PM EDT)
Michael Mendelsohn (8.10.2004 @06:37:00 PM EDT)
Jean-Pierre Battaille (8.11.2004 @12:42:08 AM EDT)
Maria Rodionova (8.11.2004 @06:05:00 AM EDT)
Nathaniel Litton (8.11.2004 @07:46:31 AM EDT)
John Ritson (8.11.2004 @08:15:52 AM EDT)
Dharmadeep Muppalla (8.11.2004 @09:22:28 AM EDT)
Nachiket Bapat (8.11.2004 @07:15:39 PM EDT)
Victor Chang (8.12.2004 @03:27:44 AM EDT)
Clive Tong (8.12.2004 @12:41:08 PM EDT)
Libin Shen (8.12.2004 @02:40:00 PM EDT)
Nicholas Kleszczewski (8.12.2004 @04:40:00 PM EDT)
Steve Powell (8.13.2004 @10:26:01 AM EDT)
Kim Jinhong (8.13.2004 @10:32:06 AM EDT)
Joe Riel (8.13.2004 @09:09:48 PM EDT)
Frank Mullin (8.15.2004 @10:39:45 AM EDT)
Renaud Bauvin (8.18.2004 @01:24:45 PM EDT)
Bill Webb (8.18.2004 @06:06:21 PM EDT)
Markus Nauroth (8.21.2004 @05:09:26 PM EDT)
Jimmy He (8.22.2004 @02:56:36 PM EDT)
Irem Koprulu and Atilla Eryilmaz (8.22.2004 @08:20:54 PM EDT)
Dion K Harmon (8.25.2004 @10:49:00 AM EDT)
Avnish Miduthuri (8.25.2004 @02:35:00 PM EDT)
Atif Hussain (8.26.2004 @02:10:42 AM EDT)
Daniel Bitin (8.26.2004 @04:02:05 AM EDT)
Raicho Tchalkov (8.26.2004 @06:41:28 AM EDT)
R. Nandakumar (8.26.2004 @10:33:50 AM EDT)
Divyesh Dixit (8.26.2004 @11:19:31 AM EDT)
Blake Eastman (8.26.2004 @03:26:33 PM EDT)
Renato Fonseca (8.27.2004 @10:21:49 PM EDT)
Ariel Flat (8.29.2004 @06:22:44 AM EDT)
Fabio Negroni (8.29.2004 @06:29:09 PM EDT)
Vedpal Singh (8.30.2004 @02:52:54 AM EDT)
Paul Botham (8.30.2004 @12:56:23 PM EDT)
Wolfgang Kais (8.31.2004 @02:48:35 AM EDT)
Andy Lowry (8.31.2004 @03:08:48 PM EDT)
Forrest Mcclellan (8.31.2004 @06:23:06 PM EDT)

Attention: If your name is posted here and you wish it removed please send email to the webmaster.