1 + 1 = ?

种瓜得瓜，种豆得豆
Plant melons and you get melons, sow beans and you get beans

The efforts made determines the achievement we will gain. In my opinion, it shows that we have indirectly agreed that 1 + 1 = 2 if we doing thing(s) accordance to the above theory. Generally, it is indeed true that if we do A, we will get A as a result.

有得必有失
Gain and Loss are coexistant

However, we can't deny that some time we do A, we get B instead of A. In this case, although we didn't get the expected result by doing A, we gained something as a return or replacement. Due to the effort made is not totally wasted, we still can consider the outcome as 1 + 1 = 2.

费时费事，得不偿失
Not Be Worth The Effort

In other cases, one may gain nothing by doing A. When this occured, no more 1 + 1 = 2, but 1 + 1 < least =" 2." style="text-align: justify;">

一石二鸟，一箭双雕
Kill Two Birds With One Stone

If we are smart enough, and always think & analyse things bilaterally, we can actually create a situation by which we able to achieve more than 1 goal with equal amount of effort. This means that by doing A, we not only get A, but also get B, or / and C or more. In this case, 1 + 1 > 2. In my opinion, the "Win-Win Situation" is a good example of 1 + 1 > 2.