 Posers and Puzzles

1. 06 Sep '07 02:01
Anyone know how to prove this to be true(even though it's not). A math teacher proved it to my math class. Everything made sense and no one could find the falacy.
2. 06 Sep '07 03:306 edits
Originally posted by smw6869
Anyone know how to prove this to be true(even though it's not). A math teacher proved it to my math class. Everything made sense and no one could find the falacy.
If there is a general formula involved in the proof, make sure division by zero isn't happening because that isn't allowed. So for example the classic case of the fallacy of 1=2 (which is very similar to yours)
step 1
Let a = b
step 2 Multiply both sides by a:
aa = ab
step 3 which is the same as:
a^2 = ab ( "a squared equals a times b" )
step 4 Add the quantity ( a^2 - 2ab) to both sides:
a^2 + (a^2 - 2ab) = ab + (a^2 - 2ab)
step 5 simplifying both sides we get:
(a^2 + a^2) - 2ab = a^2 + (ab - 2ab)
2(a^2) - 2ab = a^2 - ab
2 (a^2 - ab) = a^2 - ab
step 6 divide both sides by (a^2 - ab):
2(a^2 - ab) / (a^2 - ab) = (a^2 - ab) / (a^2 -ab)
step 7 cancel out like terms in num.&denom:
2 = 1 !!!

Two equals one? Impossible! What's the catch? The catch is, our very first assumption is Let a= b, and if that's true then the quantity (a^2 - ab) = (a^2 - a^2) = 0, and we are not allowed to divide by zero which is what we do in our "proof" in step 6. The proof is not allowed. No division by zero.

I bet this is the trick that is happening in your false proof of 2+2=5.

(sorry for all the edits, but I had to work out some formatting issues)
3. 06 Sep '07 11:47
Great
4. 06 Sep '07 14:34
This is generally to do with rounding:
2.4 rounds to 2
2.4+2.4=4.8 which rounds to 5.

If you round everything: 2+2=5
5. 06 Sep '07 19:24
An alternative to this one I came across is this...

2+2=10

This is mathematically true, and breaks no rules, but I've left out one piece of information. What's the information I've left out?
6. 06 Sep '07 19:40
Originally posted by agryson
An alternative to this one I came across is this...

2+2=10

This is mathematically true, and breaks no rules, but I've left out one piece of information. What's the information I've left out?
base 4
7. 06 Sep '07 19:42
Originally posted by Mephisto2
base 4
Got it. Though when i was told it, the dumbass mixed them up and said
2+2=5... in base four. I slapped him over the back of the head.
8. 07 Sep '07 08:19
9. 07 Sep '07 09:04
binary

but 10 x 10 = 100 is less clear 😵
10. 07 Sep '07 16:06
6+5=3 anyone?
11. 07 Sep '07 21:17
mod 8
12. 09 Sep '07 13:32
no its not, if it's binary then it would either be 10 + 10 = 4 or 10 = 10 = 256; all depends where the other six zeros are
13. 09 Sep '07 13:321 edit

anyone who's a musician should get that
14. 09 Sep '07 13:47
Originally posted by eatmybishop
no its not, if it's binary then it would either be 10 + 10 = 4 or 10 = 10 = 256; all depends where the other six zeros are
In binary there is no '4' or '256'

10+10=100 is quite correct (ie 2+2=4 in decimal)

10x10=100 is true in any base.
15. 12 Sep '07 18:38
Originally posted by wolfgang59
In binary there is no '4' or '256'

10+10=100 is quite correct (ie 2+2=4 in decimal)

10x10=100 is true in any base.
no its not, you're wrong...

i was under the impression is was binary to decimal.. so you're right there, there is no 4 or 256 in binary... however you're still wrong...

in binary, it would be 10+10=10... you are wrong to say 100, its not, 1 + 1 = 1 or 0 + 1 = 1, 0 + 0 = 0.... there is no additional digit.... mr dumb!