In a harmonic progression, the reciprocals of the terms form an arithmetic progression. The reciprocals of 2 and 4 are 1/2 and 1/4. The common difference is -1/4. Therefore, the third term's reciprocal is 1/4 - 1/4 = 0, which means the third term is 1.

In a harmonic progression, the reciprocals of the terms form an arithmetic progression. The reciprocals of the first two terms are 1/2 and 3/4. The common difference is 1/4, so the reciprocal of the third term is 1/2 + 1/4 = 3/4. Therefore, the third term is 1/(3/4) = 4/3.

The reciprocals of the first two terms are 1/3 and 1/6. The common difference is 1/6 - 1/3 = -1/6, which is incorrect. The correct common difference is 1/3 - 1/6 = 1/6.

The reciprocals of 3 and 6 are 1/3 and 1/6, which are in arithmetic progression.

The reciprocals of the terms are 1/3 and 1/6. The common difference is (1/6 - 1/3) = -1/6. The third term's reciprocal will be 1/6 - 1/6 = 0, which means the third term is 1/12, thus the answer is 12.

The reciprocals of the terms are 1/4 and 1/2. The common difference is 1/2 - 1/4 = 1/4.

The reciprocals are 1/4 and 1/8. The common difference is 1/8 - 1/4 = -1/8. The third term's reciprocal will be 1/8 - 1/8 = 0, hence the third term is 16.

The reciprocals are 1/4 and 1/8. The common difference is 1/8 - 1/4 = -1/8, which means the common difference of the corresponding arithmetic progression is 1/8.

The first term is 5, and the second term in the harmonic progression corresponds to the reciprocal of the second term in the arithmetic progression, which is 5 + 2 = 7. Thus, the second term is 1/7.

The reciprocals are 1/5 and 1/10. The common difference is 1/10 - 1/5 = -1/10, which is the difference in the arithmetic progression.

The reciprocals are 1/5 and 1/10. The common difference is -1/10. The reciprocal of the third term is 1/10 - 1/10 = 1/15, so the third term is 15.

The nth term of a harmonic progression can be expressed as 1/(1/a + (n-1)d) where d is the common difference of the corresponding arithmetic progression.

The sum of the first n terms of a harmonic progression can be expressed as 2n/(a+b) where a and b are the first two terms.

The harmonic mean of a set of numbers is the reciprocal of the arithmetic mean of their reciprocals.

The terms of a harmonic progression are the reciprocals of the terms of an arithmetic progression.

Harmonic progression can include fractions, as it is defined through the reciprocals of an arithmetic progression.

Harmonic progressions can contain negative numbers, but the terms themselves must be positive to maintain the definition of harmonic sequences.

The sum of the terms in a harmonic progression is not necessarily an integer, as the terms can be fractions.

The sum of the first n terms of a harmonic progression diverges as n approaches infinity, hence it is not finite.

The sequence 2, 4, 8 does not have reciprocals that form an arithmetic progression, hence it cannot be a harmonic progression.

The sequence 1, 1/2, 1/3 has reciprocals 1, 2, 3 which are in arithmetic progression, thus it is a harmonic progression.

In a harmonic progression, terms cannot be zero as it would make the reciprocal undefined.

In a harmonic progression, the terms can be negative as long as their reciprocals form an arithmetic progression.

In a harmonic progression, the terms can indeed be negative, as the definition does not restrict the terms to positive values.

In a harmonic progression, the reciprocals of the terms indeed form an arithmetic progression.