Question

PLZZZ ANSWER THIS QUESTION 4 WITH PROPER EXPLAINATION

Answer 1

speed of train is 30m/s
it takes 500/30 seconds for the front of train to pass thru bridge (coz speed = distance/time)
and 100/30 for the rest of it to pass

so total time is
500/30 + 100/30 = 600/30 = 20 seconds.