There are slight differences between ‘amount of’, ‘quantity of’ and ‘number of’

Amount of

Amount of is used for things you can’t measure. It is usually in front of a singular word.
I have a reasonable amount of work this week. Work – singular non-count word
He has a certain amount of respect for the sales team. Respect – singular non-count word

Quantity of

Quantity of is used for things that you can measure. It is usually used to refer to inanimate objects.

The police appropriated a large quantity of money after the raid.

The quantity of cars imported from Japan has increased. Cars – plural count word

Number of

Number of is usually used before a plural count noun. It can be used for both inanimate and animate objects.
A large number of tourists to Malta come from the continent.

The cargo of the ship that ran aground consisted of a large number of computer consoles.

Lesson by Tristan, teacher at EC Malta English school

Now complete the following with the correct phrase:

• 1. We are going to need a large _ paper next week because of the conference.
  quantity of
  number of
  amount of

• 2. They need to increase the _ meat consumed per person.
  number of
  quantity of
  amount of

• 3. I don’t need that much _ sleep.
  quantity of
  amount of
  number of

• 4. The company usually refuses a large _ of applicants every year.
  number of
  amaount of
  quantity of

• 5. I have a certain _ contempt for people like David.
  quantity of
  number of
  amount of

• 6. We have tackled a huge _ work this week.
  quantity of
  amount of
  number of