An unknown number of demonstrators were arrested.

不知多少示威者被逮捕了。

《柯林斯英汉双解大词典》

When most of us get a text message on our cell phone from an unknown person, we usually say "sorry, wrong number!"

当我们收到陌生人的短信时, 我们通常会说：“对不起, 你发错了！”

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The letter "x" often represents an unknown number in some Math exercises.

在一些数学练习中，字母“x”通常代表一个未知数。

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Diakite,who is also known as Toumba, escaped the attack and is still at large with an unknown number of soldiers from the presidential guard.

VOA: standard.2009.12.07

But if Apple cuts its profit margins to do it then jobs (some number, unknown) will disappear somewhere else as a result of the reduction in those profits and the value of Apple as a company.

FORBES: If Apple Onshored iPad Production it Would Create 67,000 American Manufacturing Jobs!

About 31 Japanese companies had offices in the buildings employing an unknown number of staff.

CNN: Asia pledges cooperation in hunt for attackers

There could be an unknown number of other sports pitches that have been lost, it said.

BBC: Olympics legacy: How can we encourage kids into sport?