subject-verb-agreement
1)Five and five make ten.
2)Five and five is ten.
I am wondering why 'Five and five makes ten' is incorrect. Even though I know that 'Five and five make ten' is correct, I am unable to explain the reason to somebody in case I need to do so. Why 'five and five' in the second sentence is treated as singular while 'five and five' in the first is treated as plural?
Although what we need are is possible in some cases, in this case it's a poor choice. Why? Because all three what we needs refers to the same thing, and that thing is either singular or plural, not both. It's quite strange to refer to it first as though it's plural, then as though it's singular.
The best choice is to use is all three times:
What we need isn't protests.
What we need is new generations able to voice their opinions.
What we need is Chinese men and women who are eloquent speakers of foreign languages.
The parallelism is stronger rhetorically in any case.
Besides which, is is the more common choice overall. Take a look at this chart of four n-grams in the Google Books corpus:
From this chart, it seems that is is eight times more common than are; and specifically with negatives, it's ten times more common. So both occur, but is is clearly favored.
It is grammatically incorrect, but most people think it is natural and don't care.
The simple subject is thing, which is singular, so the verb must be singular to agree with it. Notice that in the subordinate clause, scares is singular, agreeing with thing.
The speaker got confused because it seems strange to say that a singular thing "is" a plural like oranges. That's more than one orange, right? Perhaps the speaker could revise the sentence so the subject is "the things that scare me the most". But there are two problems with that. First, the idiomatic phrase is "the thing that scares me the most". If you say "the things that scare me the most", that's weaker, because then you aren't pointing out the #1 scariest thing. Second, the speaker starts saying the sentence before choosing the main verb. By the time the speaker has said "The thing that scares me the most", it's too late to change it. At that point, the speaker sees oranges coming up ahead, and scrambles to choose the verb. "Is" sounds wrong because of oranges; "are" sounds wrong because of thing. Oh no!! There's no time to think this through, so the speaker compromises and chooses a verb to agree with oranges, dimly sensing that something is wrong.
And then life goes on.
Best Answer
In math, we speak of equations or equalities
5 + 5 = 10
The equation, the statement that two expressions yield the same value, can be expressed in natural language in several ways, the first, drawing attention to the equality:
the second, drawing attention to the operation of addition:
P.S. We can also say
Five plus five make ten, or add up to ten, or give ten.
The decision to use a singular or plural verb hangs on whether the speaker has in mind two distinct elements ("five ... five", understanding plus to mean "and") or a single expression as the subject, i.e. a singular noun linked by the word plus with another noun, as in "five augmented-by five ...".
These are also valid and grammatical:
depending on the speaker's attitude towards the subject, whether it is compound, consisting of two nouns conjoined, or a single expression.