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》

Does the calculated value compare with the known quantity?

是否与计算值比较噪。

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The last step is to judge whether the estimated quantity compares with a known quantity.

最后一步是判断估计量相比有噪。

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Hardly an inspiring way of choosing a candidate, but Republicans apparently like a known quantity.

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G. was such a known quantity, how on Earth is someone going to fill those shoes?

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By contrast, the PPI payments were, by the time of the Budget, very much a known quantity.

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