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What does 2 + 2 =?


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If these are absolute 2's (2.000000 to an infinite number of zeros) the answer is exactly 4 - expressed by what number system you prefer: 100 in binary, etc.

But if it's a measured number, 2 + 2 = at least 3.5 and less than 4.5 under standard scientific math.  It can also be mean at least 3 and 5 or less in extreme circumstances.

If it's a measured number, the single digit (called one "significant figure") indicates it's measured to the nearest whole number of the measurement unit, so it's between 1.5 and 2.5 (in science, .5 numbers are rounded to the nearest even number).  So being told only "2" and not "2.0," "1.9," "2.1," etc. we might be adding as little as 1.5 + 1.5 or as much as 2.5 + 2.5.

Scientifically and in serious mathematics, adding numbers together normally requires that the answer be rounded to the lowest place all the added numbers have in common.  So 2.4 + 2 = 4 in measured numbers, NOT 4.4 because we don't know what the first decimal place in "2" is. It could be 2.2, it could be 1.5, etc.

But 2 + 2 = 4 has an answer with just one significant figure, so it would be correct as the answer to a measured number addition of 2's.

Still, that "4" can mean anything from 3.5 to 4.499999etc.

So, the all encompassing answer is that 2 + 2 = at least 3.5 and less than 4.5 in standard math and between 3 and 5 in extreme math.

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