measure expressions - 100 apples are/is considered as a large number of apples

Should I use is or are in this sentence?

100 apples are/is considered as a large number of apples.

Answer

Subjects expressing periods of time, amounts of money, or quantities may take either singular or plural verbs depending on whether [they] represent a total amount or a number of individual units. For example, "Four weeks is not enough vacation time" and "Two days have passed since I asked for your response." (Section 2 paragraph 8 of source)

In your example, as the complement ("a large number") is singular, the subject represents a total amount, and so is treated as a singular. I would use is.

Compare that with

100 apples are rolling down the hill.

Here the 100 apples represents 100 individual units, so I use the plural.

The source notes that this is a tricky point, and there is variation among native speakers.

Rephrasing can avoid this issue:

One hundred is considered to be a large number of apples

We consider a hundred to be a large number of apples.