'two and two are four' vs. 'two and two is four' -- What's correct?

[Narayanan krishnaswamys]

Which one, of these two, is correct?
a) Two and two is four.
b) Two and two are four.

[Alan]

Both are used and are acceptable. Two and two is 4 suggests you are thinking of the calculation and Two and two are 4 suggests you are thinking of the separate numbers.
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