train traveling north @ 60mph. one hour later, another train leaves @ 70mph. how far away before second train catches up? t

8 years agoright so this is a bit harder to parse

8 years agoso basically the second train has caught up once the distances they've traveled are exactly equal

8 years agook so in one hour, once the second train leaves, the first train has a 60mph*1hr head start

8 years agoso it's gone exactly 60 miles already

8 years agoso from that point on, we're basically solving for some time T

8 years ago70*T - 60*T = 60 (the head start being 60mph)

8 years agoor in time T, when they have traveled the same distance, we know that 70*T = 60 + 60T

8 years agoso 70T - 60T = 60 = 10T

8 years agoso 10T = 60

8 years agoIn six hours, they would have traveled the same distance

8 years agoso now let's check this:

8 years agoIn 6 hours from the original 1 hour, the first train has traveled 7hours

8 years agoso it's traveled 7 hours * 60mp/h = 420 miles

8 years agothe second train has traveled 6 hours total. so 6 hours * 70mph = 420miles

8 years agowhich is exactly the point the second train passes the first

8 years agomake sense?

8 years agoyep!!

8 years agoawesome =)

8 years ago