3） 表示金钱，时间，价格或度量衡的复合名词作主语 时，通常把这些名词看作一个整体，谓语一般用单数。(用复数也可，意思不变。) 
　 Three weeks was allowed for making the necessary preparations. 
　 Ten yuan is enough. 

五、指代意义决定谓语的单复数
1） 在代词what, which, who, none, some, any, more, most, all等词的单复数由其指代的词的单复数决定。 
All is right.　 (一切顺利。) 
All are present.(所有人都到齐了。) 

2） 集体名词作主语时，谓语的数要根据主语的意思来决定。如family, audience, crew, crowd, class, company, committee等词后用复数形式时，意为这个集体中的各个成员，用单数时表示该个集体。 
His family isn’t very large.他家不是一个大家庭。 
His family are music lovers.　他的家人都是音乐爱好者。 
　 　但集合名词people, police, cattle, poultry等在任何情况下都用复数形式。 
Are there any police around? 

3）有些名词，如variety, number, population, proportion, majority 等有时看作单数，有时看作复数。
A number of +名词复数+复数动词。 
The number of +名词复数+单数动词。 
A number of books have lent out. 
The majority of the students like English. 

六、与后接名词或代词保持一致
1） 用half of, part of, most of, a portion of 等词引起主语时，动词通常与of后面的名词，代词保持一致。 
Most of his money is spent on books. 
Most of the students are taking an active part in sports. 

2） 在一些短语，如 many a 或 more than one 所修饰的词作主语时，谓语动词多用单数形式。但由more than… of 作主语时，动词应与其后的名词或代词保持一致。 
　 　Many a person has read the novel.　许多人都读过这本书。 
　 　More than 60 percent of the students are from the city.百分之六十多的学生都来自这个城市。