Hi,

Which is correct?

The HIGHER the number of people in the auditorium, the better the sales.

The LARGER the number of people in the auditorium, the better the sales.

Thank you in advance!
Both of those are OK, but neither is as common as 'the greater the number'. However, I would dump the lot and choose the more colloquial:

The more people there are in the auditorium, the better the sales.