Graham Broadley asks:
Should it be: where is my fifty dollars or where are my fifty dollars. Most people would say is, would they be correct? Surely are would be more correct, being plural, right?
When the subject stands for a definable unit, such as money, measurement, time, organization and food combinations, the verb is indeed singular:
Where is my fifty dollars?
Three months is not enough time to write such a long novel.
Ham and eggs is my favorite breakfast.
According to the Southern Writing Center guide (pdf):
When the compound subject is joined by and but represents a single idea or person, the compound subject is treated as a unit and a singular verb is used.
Example: Ham and eggs is a popular breakfast dish. (Ham and eggs refers to a single dish.)
When a compound subject joined by and is preceded by each or every, a singular verb is used.
Example: Every student and teacher has to wear a uniform. (The singular verb has agrees with every, not student and
The careful writer will make sure that the singular verb is used with such compounds.