When does one and one not equal two?

When they are subtracted or the number 11

For large values of one -Engineering answer
When not in base 10 - Math answer



or
if you make a mathematical error and divide by 0

a = 1
b = 1

a = b
a2 = b2
a2 - b2 = 0
(a-b)(a+b) = 0
(a-b)(a+b)/(a-b) = 0/(a-b)
1(a+b) = 0
(a+b) = 0
1 + 1 = 0
2 = 0
1 = 0
1 + 1 = 1

http://mathforum.org/dr.math/faq/faq.false.proof.html

nice job on the answers so far, theres a couple more that work too

not necessarily math based

can you think of what they are?

nice job on the answers so far, theres a couple more that work too

not necessarily math based

can you think of what they are?

when one or both of the 1's are negative integers

when you are talking about sex... :p