The Washington Post Co. on Friday reported a 50 percent drop in second-quarter earnings, with revenue continuing to plummet in the Kaplan Higher Education Unit and both the online and print operations of the newspaper division seeing declines in advertising revenue. Overall profits for the quarter that ended July 3 totaled $45.6 million ($5.74 per share), the company said, compared with $91.9 million ($10.00 per share) a year earlier. Revenue increased at The Post Co.’s television broadcasting and cable television divisions.