Is wrong to say "two and two are not five"...? [duplicate]

Solution 1:

The sentence two twos are four is correct, but although it is a common English phrase, it is not mathematical - in actual mathematics, the equations is not pronounced that way.

In mathematics, the equal sign is pronounced as equals or simply is.

It denotes that everything on the left equals everything on the right, hence the singular.

However, in mathematics, no-one will ever pronounce 2 x 2 = 4 as two twos are four.

Two times two equals four
Two times two is four

Are both acceptable, and indeed, the singular is used to indicate that the parts on the left and the right of the equal sign are seen as complete, whole, singular expressions. (So even 7 times 5 plus 3 divided by 12 minus 2 is seen as a singular expression.)

The simplified two twos are four is in itself correct, as it strays from the strict mathematical domain. It aims at visualizing for children that 2 x 2 = 4 can be seen as two occurrences of a concept "2". In that case, since we are actually counting them, the plural is correct, in exactly the same way as we say

Two horses have 8 legs. (not has!)