<p>I put 1600. Ok so the train goes in the tunnel. The tunnel is 1400 m long. so we got 1400 down. The train first touches the tunnel at its front. But the question wants how long did the train travel to get its whole rear out the hole. So thats an extra 200 m that it has to haul. That means it take 1400+200=1600 right?? why would u subtract to get 1200??</p>
<p>but you dont mention how long the train is!</p>
<p>**** nvm i got it</p>
<p>no the question wants how long did it take for the train to travel with it’s head touching the front of the tunnel, to it’s head touching the end of the tunnel. we know that it takes 1 min and 10 secs for the train to travel with it’s head touching the front of the tunnel to it’s rear touching the end of the tunnel. we can figure out that it took 1 min for the train’s head to touch the end of the tunnel, because the length of the train is 200m. then we subtract 20 * 70 secs - 20 * 10 secs which is 1400 - 200 = 1200.</p>