Question

define adjective of quantity with its examples.

Answer 1

it means the adjective words showing a quantity of something.
ex. this packet weighs 49 grams.
i want a kilo of potatoes

Answer 2

Heya
Here is your answer
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Adjective showing the quantity of noun or pronouns are called adjective of quantity

They answer of the question HOW MUCH

Examples: 

He gave me ten toffees

here ten is adjective of quantity

Similarly

All students are present

here All is adjective of quantity

You don't have much water

here much is adjective of quantity
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Hope it helps! ^_^