From a mathematical point of view, 1+ 1 = 2 is a basic assumption, which is the basis of mathematics. Without it, all theorems cannot be established.

There are many answers, which can be understood as:

A glass of water with a glass of water or a glass of water.

This is relative. One of 1+ 1 is relative to the original "unit" or "quantity", and so is "2" in "=2". And what you said is equal to "1". This "1" is not defined by the original unit, but a new "unit".

⒊ 1+ 1>； 2. For example, if you cooperate with others, it may be greater than 2, which you can't accomplish alone in twice the time. It may be less than 2, and it can be completed in less than twice the time.

Not all efforts can be rewarded.

One day plus one night equals a whole day, but not two days.

Even if people hope that one plus one equals two, they may not be able to do things perfectly, the error is absolute, and the plan can't keep up with the changes.

Nothing is absolute, some things look alike on the surface. If you don't combine them at will according to the specific actual situation, sometimes you will be self-defeating because it is not suitable, and you won't get the results you take for granted.