About the usage of "quantities of " and " a quantity of ", 1. Quantities of books ARE on the floor. ( is / are ) A quantity of books ARE on the floor. ( is / are ) 2. Large quantities of water ARE wasted. ( is / are ) A large quantity of water IS wasted. ( is / are ) Is = usually used in a singular form Are = usually used in a plural form I think question two may be a trick question, or a question testing your concept of grammar. You see in question four that "QUANTITY" is before the use of "are" or "is". But, in question two, quantity is used earlier on in the sentence, "BOOKS" is used right before the intended words; "is" or "are", and "BOOKS" is plural. So "are" should be used.

1.A quantity of books _____is______ on the floor. 2. A large quantity of water ____is________ wasted.