Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 30-12-2011, 00:11   #1
Registered User
 
avb3's Avatar

Cruisers Forum Supporter

Join Date: Jul 2010
Location: Florida/Alberta
Boat: Lippincott 30
Posts: 9,913
Images: 1
Math is dangerous; proof 2=1

Many sailors use calculations for boat ratios, perhaps rigging, or navigation.

So, this should be easy right?

Here's a mathematical proof that appears to show that 2=1. Can you find what's wrong with it.

Let x=y
Then x^2=xy (by multiplying both sides by x)
Then x^2-y^2=xy-y^2 (by subtracting y^2 from both sides)
Then (x+y)(x-y)=y(x-y) (by factoring both sides)
Then x+y=y (by dividing both sides by (x-y))
Then y+y=y (since x=y by the original assumption)
ie. 2y=y
Therefore 2=1 (by dividing both sides by y)

Clearly 2 and 1 are not equal, what mistake was made above?
__________________

__________________
If your attitude resembles the south end of a bull heading north, it's time to turn around.
avb3 is offline   Reply With Quote
Old 30-12-2011, 00:34   #2
Registered User
 
deckofficer's Avatar

Join Date: Feb 2011
Location: Northern and Southern California
Boat: too many
Posts: 4,198
Images: 4
Re: Math is dangerous; proof 2=1

No mistake made if x=0.
__________________

__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
http://tbuckets.lefora.com/
deckofficer is offline   Reply With Quote
Old 30-12-2011, 00:35   #3
Registered User
 
Target9000's Avatar

Join Date: May 2009
Location: New Orleans LA
Boat: 74 Westsail 32
Posts: 1,379
Re: Math is dangerous; proof 2=1

Quote:
Originally Posted by avb3 View Post
Then (x+y)(x-y)=y(x-y) (by factoring both sides)

Since x = y then (x-y) is 0.
__________________
Let your heart tell you where to go, but let your brain tell you how to get there.

Sundowner Sails Again
Target9000 is offline   Reply With Quote
Old 30-12-2011, 00:36   #4
Registered User
 
Target9000's Avatar

Join Date: May 2009
Location: New Orleans LA
Boat: 74 Westsail 32
Posts: 1,379
Re: Math is dangerous; proof 2=1

Also... Math is flawless. Humans are dangerous.
__________________
Let your heart tell you where to go, but let your brain tell you how to get there.

Sundowner Sails Again
Target9000 is offline   Reply With Quote
Old 30-12-2011, 02:38   #5
Registered User
 
sctpc's Avatar

Join Date: Jul 2008
Location: Melbourne Australia
Boat: saga kan walker 31ft
Posts: 545
Send a message via Skype™ to sctpc
Re: Math is dangerous; proof 2=1

Since x=y, (x-y)=0,So it is not possible to divide any equation by zero.
__________________
May there always be water under your boat,

sctpc is offline   Reply With Quote
Old 30-12-2011, 04:06   #6
Freelance Delivery Skipper..
 
boatman61's Avatar

Community Sponsor
Cruisers Forum Supporter

Join Date: Jan 2010
Location: PORTUGAL
Posts: 20,225
Images: 2
pirate Re: Math is dangerous; proof 2=1

Seeing as none of the Maths I do on board involve Algebra...
x-y= Pointless
__________________


Born To Be Wild
boatman61 is online now   Reply With Quote
Old 30-12-2011, 04:29   #7
Don't ask if you can't handle it
 
sailorboy1's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: On the boat somewhere
Boat: Hunter 410
Posts: 12,326
Re: Math is dangerous; proof 2=1

Quote:
Originally Posted by boatman61 View Post
Seeing as none of the Maths I do on board involve Algebra...
x-y= Pointless
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is offline   Reply With Quote
Old 30-12-2011, 04:52   #8
Registered User
 
pressuredrop's Avatar

Join Date: Apr 2009
Location: West Palm Beach
Boat: Allied Seawind 30
Posts: 794
Re: Math is dangerous; proof 2=1

Quote:
Originally Posted by avb3 View Post
Then (x+y)(x-y)=y(x-y) (by factoring both sides)
cant do that...

(x+y)(x-y) = x^2 - y^2.... NOT yx-y^2....


easyyyyy.... next....
__________________
pressuredrop is offline   Reply With Quote
Old 30-12-2011, 11:34   #9
Registered User
 
capn_billl's Avatar

Join Date: Aug 2010
Location: Houston,Tx
Boat: Maxum 37'
Posts: 1,587
Re: Math is dangerous; proof 2=1

You broke several rules, 1, misuse of associative rule, 2. divide by zero.
__________________

__________________
capn_billl is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Most Dangerous Sailing / Boating Is Coastal, Not Offshore sailorboy1 General Sailing Forum 67 06-11-2011 22:39
'Texas Man Making Dangerous Voyage to Site of '67 Israeli Attack on the USS Liberty!' veprjack General Sailing Forum 9 19-08-2011 18:23
Is Boating Dangerous ? lorenzo b Our Community 93 12-08-2011 12:39



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 02:55.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.