以下两用法均可：
一、与词形保持一致（quantity 的单复数，决定谓语动词的单复数）：这种观点认为，不看aquantityof 或quantitiesof 后面接单数名词还是复数名词，只看quantity本身。即：quantity是单数，谓语动词就用单数；quantities是复数，谓语动词就用复数。即遵循“语法一致”的原则。例如：
Alargequantityofwashingmachineshasbeensold、
A great quantityofmoney was spent on the project、
Largequantitiesofbooks were sent to the village schools、
Largequantitiesofsandwerewasheddownthehillbytherain、
二、还有一种比较流行的观点，就是：a (large) quantity of或 (large) quantities of，其后均可跟不可数名词或复数名词。在句中作主语时，a quantity of接不可数名词时，谓语动词用单数形式；接可数名词复数时，谓语动词用复数形式。quantities of后接不可数名词或可数名词复数时，谓语动词都用复数形式。
Alargequantityofwashingmachineshavebeensold、
A great quantityofmoney was spent on the project、
Largequantitiesofbooks were sent to the village schools、
Largequantitiesofsandwerewasheddownthehillbytherain、