GAMEBOOMERS provides you with all the latest PC adventure computer games information, forum, walkthroughs, reviews and news.
GB Reviews Latest & Upcoming Adventure Games GB Annual Game Lists GB Interviews

BAAGS

GB @ acebook

GB @ witter

About Us
Walkthroughs free games galore Independent Games World of Adventure Patches Game Publishers & Developers GameBoomers Store
Big Fish Games Homepage    
Topic Options
#876369 - 03/27/13 09:18 AM River crossers
CanukDenis Online   content
Graduate Boomer

Registered: 11/26/00
Posts: 15385
Loc: Ottawa Ontario Canada
26 guys (named A to Z!) have to cross a river.

Only one canoe is available, and it can take at most 2 guys.

A is the fastest: takes him 1 second to row across (told you he was fast!).

Then we have B:2 seconds, C:3 seconds and so on to Y:25 seconds, Z:26 seconds.

When 2 guys are crossing, the slowest one rows (Why? To make this puzzle harder!)

What is shortest possible time to get all 26 guys across?
_________________________
We're all here because we're not all there !

Top
#876519 - 03/28/13 01:16 AM Re: River crossers [Re: CanukDenis]
CCbomber Offline
Addicted Boomer

Registered: 01/16/03
Posts: 3397
Loc: Mojave desert, California
242 sec? (not counting any time on shore)

A,B cross, A returns, 3 sec
C,D cross, B returns, 6 sec
A,B cross, A returns, 3 sec
E,F cross, B returns, 8 sec
A,B cross, A returns, 3 sec
G,H cross, B returns, 10 sec
.
.
.
W,X cross, B returns, 26 sec
A,B cross, A returns, 3 sec
Y,Z cross, B returns, 28 sec
A,B cross................, 2 sec

Total time = 242 sec

Top
#876563 - 03/28/13 07:44 AM Re: River crossers [Re: CanukDenis]
CanukDenis Online   content
Graduate Boomer

Registered: 11/26/00
Posts: 15385
Loc: Ottawa Ontario Canada
Correct.

Notice the "6 + 8 + 10 + ... + 28" series, and the "3 sec" return trips.

n = (number of crossers + 2) / 2

time = n(n+1)-6 +3(n-2) + 2 = n^2 + 4n - 10

Can be rearranged as a direct function of c (number of crossers):
time = (c^2 + 12c - 20) / 4

Slightly different if odd number of crossers.
_________________________
We're all here because we're not all there !

Top

Moderator:  Pandora, soot, Urban Worrier 

Who's Online
Key: Admin Global Mod Mod Staff  )
12 registered (Pandora, oldbroad, mabeco, manxman, cyanne, Koala, BrownEyedTigre, luv2travel, granny, 1 invisible), 53 Guests and 13 Spiders online.
Newest Members
Mr_Underhill, Lani, Rachissa, marmarmargar, deadbringer
8579 Registered Users