In the equally tempered scale to which keyed instruments have been tuned since the days of J.S.

Question:

In the equally tempered scale to which keyed instruments have been tuned since the days of J.S. Bach (1685-1750), the frequencies of successive notes C, C#, D, D#, F, F#, G, G#, A, A#, B, C from a geometric sequence, with C having twice the frequency of C(C# is read C sharp). What is the ratio r between the frequencies of successive notes? If the frequency of A is 440, find the frequency of C.