She had known Max for some years now, but he was still pretty much an unknown quantity.

她现在认识马克斯也好几年了，但是他仍然是个大大的未知数。

《柯林斯英汉双解大词典》

Are an unknown quantity.

对于他们来说是一个未知的组合。

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Unknown Quantity: a Real and Imaginary History of algebra.

《隐蔽的数量：代数的真实和想象的历史》。

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Yet as far as Channel 4 is concerned, Ahmadinejad is still an unknown quantity for most Britons.

CENTERFORSECURITYPOLICY: The ��realist�� fantasy

"It'll be a British style game and it's not the unknown quantity we could have had, " he added.

BBC: [an error occurred while processing this directive]

But in some key repertoire for the Philharmonic, Bruckner and Schumann for instance, he is an unknown quantity.

ECONOMIST: Why Berlin��s musicians don��t need a maestro