In these sentences which verb should be chosen?

The public also views/view other sculptures at the memorial.

I think Views because public is plural?

Mathematics fail/fails to explain the wall's dramatic effect.

Fail?

Views is correct -- but public views is singular.

Mathematics is also singular so takes the verb fails.

Think: He fails, They fail

Public is singular, a body of people.

You're right on the second one. Mathematics is also singular.

Yes, fails is right on the second one. I goofed.

What about this one?

Each of the walls halves are/is about 250 feet long.

I think is because each is one part

You're right. Each is singular. Each is.

In the sentence "The public also views/view other sculptures at the memorial," the verb you should choose depends on whether you are referring to the singular form or the plural form of "the public."

If you are considering "the public" as a collective noun, referring to a group as a whole, then you would use the singular form of the verb: "The public also views other sculptures at the memorial."

If you are considering "the public" as individuals within the group, you would use the plural form of the verb: "The public also view other sculptures at the memorial."

Regarding the sentence "Mathematics fail/fails to explain the wall's dramatic effect," you should use the verb "fails." In this case, "mathematics" is being treated as a singular subject, so the verb should agree with that.

So, the correct sentence would be: "Mathematics fails to explain the wall's dramatic effect."