Which is more correct to say:

  • Five and four are eight
  • Five and four is eight

My Logic teacher has sent this to us to figure out. What is written above is all the information we were given. I know that in terms of math neither is correct.

I have tried to disregard that the words are numbers and think about in in a different way. I do not know the rules for the correct use of are and is in the English language. If you can help that would be great.

marked as duplicate by Drew, tchrist, Andrew Leach Mar 1 '15 at 10:15

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  • 1
    I'm voting to close this question as off-topic because the question is apparently about formal logic, not English. – Drew Mar 1 '15 at 1:16
  • The English issue is covered elsewhere. The philosophical question (of whether the two items four and five should be considered as a single entity of the total, two entities as the consitituents of the total or nine entities as the complete set) is out of scope. – Andrew Leach Mar 1 '15 at 10:17
  • Using the first one would get you two weeks in prison if the maths police caught you. Using the second one, fourteen days. The grammar police would let them do the paperwork. – Edwin Ashworth Mar 1 '15 at 15:33

Ignoring, as you said, the use of and with numbers, and sticking with and as a logical connective, the sentence is presumably to be considered as X AND Y (is|are) Z, where you are to choose is or are. The answer is is, because the truth value Z is singular - it is true or false (or something else in, say, a 3-valued logic).

But at that level this is not an English question but a logic question, so it should be closed as off-topic, IMO.

  • So, “Peter and Paul is a pair” then? – tchrist Mar 1 '15 at 13:00
  • @tchrist: No, that doesn't use and as a logical connective. It is the context here (of a Locic class assignment) that suggests the interpretation I made (see "presumably"). – Drew Mar 1 '15 at 15:05

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