two waves of same pitch have amplitudes in the ratio 1:3. What will the ratio be of their intensities and frequencies?

Dear student,

(i) Intensity is the measure of Loudness, which  is proportional to amplitude squared
       Hence, the Ratio of loudness= $1/3^2 = 1:9$
(ii) The frequency of the sound wave has no effect on amplitude.
       so, ratios of frequency remain the same that is 1:1

Regards