perplexus.info :: Logic : Five People on Two Bridges

Five People on Two Bridges (Posted on 2005-06-25)

In the puzzle Four people on a Bridge we met four people who needed to cross a bridge at night. In this puzzle, there are five people who must cross two sequential bridges at night. As in the original puzzle, there are some hindrances:

The bridges can only support two people crossing at a time.

Each person has a different speed in which they can cross: 10 minutes, 7 minutes, 5 minutes, 2 minutes, and 1 minute.

They have only two flashlights to share among them.

What is the shortest amount of time it will take for all five people to cross both bridges?

Submitted by Erik O.

Rating: 3.8000 (5 votes)

Solution: (Hide)

27 minutes.

T(0)-T(2) 1, 2 cross the first bridge.
T(2)-T(12) 7, 10 cross the first bridge.
T(2)-T(4) 1, 2 cross the second bridge.
T(4)-T(5) 1 returns to the middle.
T(12)-T(22) 7, 10 cross second bridge.
T(12)-T(13) 1 returns to the starting point.
T(13)-T(18) 1, 5 cross the first bridge.
T(22)-T(27) 1, 5 cross the second bridge.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Puzzle Solution	K Sengupta	2022-07-19 23:59:25
10 Minute Solution	Rich	2005-09-23 08:03:50
re: Question	Erik O.	2005-08-08 19:33:43
re: Solution...?	Gururaj	2005-08-03 07:48:30
this too	mish	2005-07-23 16:29:03
i think	mish	2005-07-23 16:28:13
so much more	Tammy Roy	2005-07-12 16:53:18
10 minutes	Lacey	2005-07-05 19:19:29
Re: Solution	K Sengupta	2005-07-05 05:54:07
..Solution..	anonymous	2005-07-04 17:15:44
redo	coryann	2005-07-01 07:08:29
bridge crossing	coryann	2005-07-01 06:52:17
No Subject	K Sengupta	2005-07-01 06:42:48
Question	Amber	2005-07-01 03:17:38
only 10 mins	j441167	2005-06-29 07:21:42
re(2): solution/Mathematical solution of my theory!!/Sorry yall!!	Awdreye	2005-06-28 07:50:51
re: solution	Awdreye	2005-06-28 07:25:31
solution	Awdreye	2005-06-28 07:20:57
the answer?	Katie	2005-06-28 02:53:12
re(4): Fastest solution yet? correct?	john	2005-06-27 20:58:17
re(3): Fastest solution yet? correct?	Erik O.	2005-06-27 20:37:59
re(4): Fastest solution yet? correct?	john	2005-06-27 20:28:16
re(3): Fastest solution yet? correct?	john	2005-06-27 20:26:09
re(3): Fastest solution yet? correct?	Tristan	2005-06-27 20:24:47
re(2): Fastest solution yet? correct?	john	2005-06-27 20:13:45
re: Fastest solution yet? correct?	Hugo	2005-06-27 19:45:22
re: Fastest solution yet? correct?	Hugo	2005-06-27 19:45:21
Fastest solution yet? correct?	john	2005-06-27 19:12:32
re: answer	David Grenier	2005-06-26 02:10:22
my solution	David Grenier	2005-06-26 02:09:24
answer	j441167	2005-06-26 01:15:31
Small request	Tristan	2005-06-25 23:00:12
1 less minute	Tristan	2005-06-25 22:52:53
Solution...?	Cougar Draven	2005-06-25 22:50:40
re: 3 less	TomM	2005-06-25 21:29:30
re: answer	billiardgirlscout	2005-06-25 20:11:56
3 less	MathManiac	2005-06-25 18:11:42
Not sure if this is the best...	Ken Haley	2005-06-25 17:03:47
re(2): Answer	Ken Haley	2005-06-25 15:48:16
re: Answer	MathManiac	2005-06-25 04:34:33
Answer	Sachin	2005-06-25 03:21:15

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