IBM Research | Ponder This | June 2001 challenges

Ponder This

June 2001

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Ponder This Challenge:

(Based on a puzzle of the nineteenth century by George Lilley, brought to our attention by Amit Elazari.)

This month we once again find a goblin chasing us.

This time we are on a train, heading due east at 60 kilometers per hour.

The goblin starts out 30 kilometers due north of us.
He runs at a constant speed, but (fortunately for us) has lost the ability to plan ahead; he always heads directly towards our current position.

(A clever goblin would aim in front of us, since our train's future motion is so predictable; but our goblin is not clever.) He catches up to us after we have travelled 100 kilometers (that is, after 100 minutes).

How fast does the goblin move?

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Challenge: 06/01/01 @09:00 AM EST
Solution: 06/29/01 @05:30 PM EST
List Updated: 06/29/01 @5:30 PM EST

Marian Olteanu (06.01.2001 @ 11:48 AM EDT)

Henry Bottomley (06.01.2001 @ 1:58 PM EDT)
Hareendra Yalamanchili (06.01.2001 @ 1:28 PM EDT)
Vladimir Sedach (06.01.2001 @ 1:56 PM EDT)
Shmuel Spiegel (06.01.2001 @ 2:39 PM EDT)
Bill Schwennicke (06.01.2001 @ 3:10 PM EDT)
Ether Jones (06.01.2001 @ 9:55 PM EDT)
Yuriy Groysman (06.02.2001 @ 5:56 AM EDT)
Dharmashankar Subramanian (06.02.2001 @ 8:17 PM EDT)
Saibal Mitra (06.02.2001 @ 9:50 AM EDT)
Vince Lynch (06.02.2001 @ 11:07 AM EDT)
Sudipta Das (06.02.2001 @ 12:12 PM EDT)
Jacques Willekens (06.03.2001 @ 7:27 AM EDT)
Bill Webb (06.03.2001 @ 10:39 PM EDT)
Adam Daire (06.04.2001 @ 8:00 PM EDT)
Pritibhushan Sinha (06.05.2001 @ 9:31 PM EDT)
Robert Sides (06.05.2001 @ 10:03 PM EDT)
Vinko Marinkovic (06.05.2001 @ 12:34 PM EDT)
Bill Wepp (06.05.2001 @ 5:19 PM EDT)
Patrice De Pra (06.06.2001 @ 3:59 AM EDT)
Krishna Kumar (06.07.2001 @ 7:26 AM EDT)
Liz Savery (06.11.2001 @ 6:31 PM EDT)
liuwei (06.11.2001 @ 6:54 PM EDT)
Artus Hervé (06.12.2001 @ 10:32 AM EDT)
Jim Callen (06.12.2001 @ 2:42 PM EDT)
Stephane Higueret (06.14.2001 @ 8:34 AM EDT)
Steve Clymer (06.14.2001 @ 1:20 PM EDT)
Mark Pilloff (06.17.2001 @ 9:26 PM EDT)
Alec Klatchko (06.18.2001 @ 2:00 AM EDT)
Michel Jacquemin (06.20.2001 @ 4:57 AM EDT)
David Friedman (06.20.2001 @ 10:54 PM EDT)
Douglas Schrag (06.23.2001 @ 8:45 PM EDT)
Alexey Vorobyov (06.22.2001 @ 4:04 AM EDT)
Larry Kyrala (06.25.2001 @ 3:27 AM EDT)
gsd+cas+gdn (06.25.2001 @ 8:15 AM EDT)
Dave Biggar (06.26.2001 @ 10:10 AM EDT)
Jan van Delden (06.27.2001 @ 9:51 AM EDT)
Santhosh Bandreddi (06.27.2001 @ 5:33 PM EDT)
Suresh Kodati (06.28.2001 @ 8:19 AM EDT)
Ben Rapp (06.28.2001 @ 12:43 PM EDT)
Prithu (06.29.2001 @ 1:18 PM EDT)

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