You can
put this solution on YOUR website!"the frequency(F) of vibration of a string varies inversely with the length(L)"
__ FL=k
"a rope 15 cm long vibrates at a frequency of 128 v/s" __ 128*15=k __ 1920=k
"what would be the length of a string vibrates at 192 v/s" __ 192*L=1920