# If there are two groups with 75 and 65 as harmonic mean and containing 15 and 13 observations then the combined harmonic mean....?

##### 1 Answer

Jun 8, 2018

70

#### Explanation:

The mean of the reciprocals of the terms in the two groups are

Thus, the sum of the reciprocals of the terms in the first group is

and that of the second group is also

The sum of the reciprocals of all 28 elements is

Hence their mean is

So, the harmonic mean of all the numbers together is 70.