The library writes off a certain quantity of books each year.

图书馆每年都注销一定数量的图书。

youdao

Is it enough to spend a certain quantity of hours in front of the PC to become an Internet addict?

投入一定数量的时间坐在电脑前成为一个网虫这有必要吗？

youdao

Air is a mixture of gases with a certain quantity of solids and usually some liquids mixed in.

空气是各种气体的混合物，其中也含有一定量的固体，也往往混有某些液体。

youdao

And would it be better to buy a part on the spot market or get a supplier to guarantee a certain quantity?

ECONOMIST: Chain reaction

"If they decide that everyone needs to eat broccoli, " then the commerce clause could allow Congress to require everyone to buy a certain quantity of broccoli, the judge said.

WSJ: States Ask Judge to Throw Out Health Law