Question

There were 100 new cases of syphilis last year in a given population of 100,000 people. at that time, 500 people in this population already had syphilis. the incidence of syphilis in this population is __________.

Answer 1

Found these choices:
100 per 100,000
500 per 100,000
1,000 per 100,000
5,000 per 100,000

The incidence of syphilis in this population is 100 per 100,000.

This means that there are  500,000 people in the population and 500 of them are with syphilis.