wrt means with respect to 1. The problem statement, all variables and given/known data see attachment that contains full question. firstly read paragraph then see on question. 3. The attempt at a solution velocity of sound will be 340ms-1 wrt air or ground(since air i snot blowng). Now speed of soud wrt train A= speed of sound wrt ground - speed of train A=340-20=320. speed of soud wrt trains B= speed of sound wrt ground - speed of train B=340-30=310. there is no such option. ???? where am i doin it wrong. thnks. waiting for ur valuable reply..