Using Just Intonation and a starting point of F=340, what would the frequency of the A above that F be?
And, what would the frequency of the C above that be? Now, what is the ratio of the C to the A? (It should be a very familiar ratio).
Using Equal Temperament in A=440, and the 1.05946 (twelfth root of 2), what is the frequency of the G natural a ninth (an octave plus a whole step, or two half steps) below that A?