SOLUTION: Train a and b are traveling in the same direction on parallel tracks. Train a is traveling at 100 mph and train b is traveling at 120 mph. Train a passes a station at 7:25 am, trai

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Question 577959: Train a and b are traveling in the same direction on parallel tracks. Train a is traveling at 100 mph and train b is traveling at 120 mph. Train a passes a station at 7:25 am, train b passes the same station at 7:40 AM at what time will train b catch up with a.
I CAME UP WITH 8:05 AM

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
after passing the station, train a has a +40+-+25+=+15+ min
head start. In +15+ min, train a travels +100%2A%281%2F4%29+=+25+ mi
If I start a stopwatch when train b passes station, then
let +t+ be the time for them to meet, and d be the
distance that b has to travel until they meet
train b's equation:
+d+=+120t+
train a's equation:
+d+-+25+=+100t+
----------------
By substitution:
+120t+-+25+=+100t+
+20t+=+25+
+t+=+5%2F4+ hr
They will meet in 1 hr and 15 min, which is
7:40 AM + 1:15 = 8:55 AM
-----------------------
check:
+d+=+120t+
+d+=+120%2A%285%2F4%29+
+d+=+150+
and
+d+-+25+=+100t+
+d+-+25+=+100%2A%285%2F4%29+
+d+=+25+%2B+125+
+d+=+150+
OK