Question

if there are two groups with 75 and 65 as harmonic means and containing 15 and 13 observation then the combined HM is given by​

Answer 1

Explanation:

Combine is appropriate in the VOA quote. It is the main verb of the sentence, indicating that rates are combining with population. Combined with would be ungrammatical; the dependent clause introduced by as would have no main verb because combined would be a participle. I feel 'combine with' is the correct form.