Question

a train crosses a platform 90 m lom in 30 seconds and a man standing on the platform in 15 seconds find the speed of the train

Answer 1

what do you mean by 'lom' & 'standing on the platform in 15 sec'
if he is running with the speed of 15 sec than the answer would be 15 secs.
or if he is actually standing the would be 30 secs