n.数量，总数（amount的复数）
v.总和（amount的第三人称单数形式）
例句：n.数量
He needs that amount of money to survive.他需要那笔钱来维持生活。
例句：v.总计
Counsumer spending on sports-related items amounted to $9.75 bilion.
消费者在体育用品上的消费总共达到了97.5亿美元。

a variety of 和 varieties of 的谓语动词用法

1：a variety of + 复数形式，谓语动词用单数：
I have a variety of books at home.
Society is made up of a variety of people.
A variety of other drying places was devised.

2：varieties of + 复数形式，谓语动词用复数
We offer over 100 different varieties of Corn Snakes.
Varieties of Lattices .
New Varieties of Food Additives, which were deliberated ......

类似这类量词都是一致的，比如a great amount of 和 great amounts of.