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A man on a railroad platform observed that a train passed by the point where he was standing in 10 seconds, and that the same train passed completely through a station, which is 308 meters long, in 24 seconds. How long was the train and how fast was it going? Thanks for help.

 Dec 15, 2016

Best Answer 

 #4
avatar+129840 
+5

A man on a railroad platform observed that a train passed by the point where he was standing in 10 seconds, and that the same train passed completely through a station, which is 308 meters long, in 24 seconds. How long was the train and how fast was it going? Thanks for help.

 

Let L be the length of the train  [ in meters ]

 

Then......in the first situation......it's rate can be modeled by :    Distance traveled / time =

rate  =  L /10   

 

In the second situation.....if we consider the back of the train, it travels [ L + 308] m in 24 seconds   = rate

 

So.......equating rates, we have that

 

L / 10  = [ L + 308] / 24   cross multiply

 

24 L   = 10 [ L + 308}    simplify

 

24 L  = 10L + 3080

 

14L  = 3080

 

L =  220 m

 

And we can use L/ 10 to find its rate  = 220 m / 10 s    =  22 m/s

 

 

 

 

cool cool cool

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  :

 Dec 16, 2016
 #1
avatar+118654 
+5

A man on a railroad platform observed that a train passed by the point where he was standing in 10 seconds, and that the same train passed completely through a station, which is 308 meters long, in 24 seconds. How long was the train and how fast was it going? Thanks for help.

 

I drew a pic to help me think about it.

 

\(speed=\frac{308m}{14sec}\\=\frac{308*60*60}{14*1000}=79.2km/hour\\~\\ \text{length of train}=\frac{308m}{14sec}\times 10sec=220m\)

 Dec 15, 2016
 #2
avatar+14985 
+5

A man on a railroad platform observed that a train passed by the point where he was standing in 10 seconds, and that the same train passed completely through a station, which is 308 meters long, in 24 seconds. How long was the train and how fast was it going?

 

\(train \ l_t\)

\(speed \ v\)

 

\(station \ l_s=308m\)

\(platform-time \ t_p=10sec\)

\(station-time \ t_s=24sec\)

 

\(v\times t_p=l_t\)

 

\(v\times t_s=l_t+l_s\)

 

\({\large v=\frac{l_t}{t_p}=\frac{l_t+l_s}{t_s}}\)

 

\(\large \frac{l_t}{10sec}=\frac{l_t+308m}{24sec}\)

 

\(24l_t=10l_t+3080m\)

 

\(14l_t=3080m\)

 

\(l_t=220m\)   Train length

 

\(\large v=\frac{l_t}{t_p}=\frac{220m}{10sec}\times\frac{km}{1000m}\times \frac {3600sec}{h}\)

 

\(v=79.2\ km/h\)   Speed

laugh  !

 Dec 15, 2016
edited by asinus  Dec 16, 2016
 #3
avatar
+5

Let the speed of the train=S,
Let the Length of the train =L, so we have:

L/10 = S, and
[308+ L]/24  =L/10, solve for L
L=220 meters long
S=22 m/s=speed of train=79.2 km/h

 Dec 15, 2016
 #4
avatar+129840 
+5
Best Answer

A man on a railroad platform observed that a train passed by the point where he was standing in 10 seconds, and that the same train passed completely through a station, which is 308 meters long, in 24 seconds. How long was the train and how fast was it going? Thanks for help.

 

Let L be the length of the train  [ in meters ]

 

Then......in the first situation......it's rate can be modeled by :    Distance traveled / time =

rate  =  L /10   

 

In the second situation.....if we consider the back of the train, it travels [ L + 308] m in 24 seconds   = rate

 

So.......equating rates, we have that

 

L / 10  = [ L + 308] / 24   cross multiply

 

24 L   = 10 [ L + 308}    simplify

 

24 L  = 10L + 3080

 

14L  = 3080

 

L =  220 m

 

And we can use L/ 10 to find its rate  = 220 m / 10 s    =  22 m/s

 

 

 

 

cool cool cool

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  :

CPhill Dec 16, 2016
 #5
avatar+129840 
+5

LOL!!!!.......looks like we ALL had the same "Train of Thought"

 

 

 

 

cool cool cool

 Dec 16, 2016
 #6
avatar+118654 
0

I liked this question - it kind of looked scary but it was really rather simple :))

And

Chris, it is dinner time and I would rather have a sushi train than a train of thought :))

 Dec 16, 2016

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