Unknown quantity

Whatever he had learned of himself was here of no avail. He was an unknown quantity.

. . . the Evening Post of this city to refer to him recently as "the young Belgian painter," and to the general public he is an unknown quantity.

The big French diesel is something of an unknown quantity, whereas many French-built electric locomotives developing 3,000 h.p. and more have been well proved in service.

In spite of more than three decades of public service, I knew I was an unknown quantity to many of my countrymen and to much of the world when I assumed office.

Amin Gemayel, it is felt here, is an unknown quantity and it is impossible to predict how he will act.

[H]e was still an unknown quantity – a young, untested figure.

Many of the applications of mathematics require that you identify an unknown quantity, assign a variable to that quantity, and then attempt to express another unknown quantity in terms of that variable.

So promising was the Skunk Works' stealth cruise missile offering, the USAF ordered an unknown quantity of these missiles under a highly classified program dubbed Senior Prom.