Harmonic Mean (H.M.)

If three quantities are in harmonic progression, then the middle quantity is called the harmonic mean between the other two.

Example:

1/3, 1/7, 1/11 are in H.P., then 1/7 is the middle term. Hence 1/7 is the harmonic mean between 1/3 and 1/11.

To find the harmonic mean between two given quantities

Let H be the harmonic mean between the quantities a and b.