* Weight of a Quarter: A US quarter weighs 5.67 grams.

* Quarters in $400: $400 is equal to 1600 quarters (400 / 0.25 = 1600).

* Total Weight: 1600 quarters * 5.67 grams/quarter = 9072 grams

Therefore, $400 in quarters weighs 9072 grams.

Here's the weight in other units:

* Kilograms: 9.072 kilograms (9072 grams / 1000 grams/kilogram)

* Pounds: 20 pounds (approximately) (9072 grams / 453.592 grams/pound)