Let speed of the train = $$10x$$ m/s Length of train = $$l$$ m Time taken to cross the pole = 6 sec Using, $$speed = frac{distance}{time}$$ => $$10x = frac{l}{6}$$ => $$x = frac{l}{60}$$ Now, 60% of the speed = $$frac{60}{100} imes 10x = 6x$$ m/s Length of platform = 240 m Acc. to ques, => $$6x = frac{240 + l}{15}$$ => $$6 imes frac{l}{60} = frac{240 + l}{15}$$ => $$frac{l}{10} = frac{240 + l}{15}$$ => $$15l = 2400 + 10l$$ => $$15l - 10l = 5l = 2400$$ => $$l = frac{2400}{5} = 480$$ m