Sony actually did reveal the split of “Interview” rentals and purchases, because algebra

The online release of “The Interview” fared surprisingly well for Sony Pictures, as the company announced total revenues of $15 million from approximately 2 million sales and rentals. The company didn’t provide a breakdown between $15 sales and $6 rentals, but as teacher Dan Myer pointed out, it didn’t have to—a bit of simple algebra does the job.

Here’s the equation, with x=the number of rentals (and “2,000,000 – x” = the number of sales)

6x + 15 (2,000,000-x)=15,000,000

Solving the equation, x=1.67 million rentals, which means there were 330,000 downloads.

Here’s a link to the math, via Wolfram Alpha (and Daring Fireball).

Read this next: Everything we know about how people watched “The Interview” and what it means for the future of internet video