Math question

[oreoeater82]

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Can someone help remind me how to do a simple "train problem"?

for example, if train A leaves the station traveling at a constant 50 mph and train B leaves its station going 25 mph constantly.... at what time or how far from station A will the two trains meet if they are 100 miles apart?

 

[klutzy1987]

are they leaving from the same station or and headed in the same direction or did they leave from from different locations and are headed towards each other??

 

[oreoeater82]

how would you do either?

 

[vsun]

i think they are traveling toward each other
if stations are 100 mi apart
50mph train starts one side and 25mph train on other side
therefore the time each travels to meet must be the same
and the sum of distance they travel is 100
so
50mph (x hr) + 25mph (x hr) = 100mi
solve for x to get time each train traveled to meet up = 1.3 hr

is that right?

 

[vsun]

if trains were leaving from same station
and u wanted to know when they would be 100 mi apart
then the dist between them would be 100 at a certain time.
and the time that happens is same for both trains

so u would do
50 mi/ hr * (x hr) - 25 mi/hr * (x hr) = 100 mi
so the difference in distance is 100 mi
and u solve for x to get the time that happens
x = 4hrs i think.

 

[vsun]

Ok i got a problem
suppose two train stations were 100 mi apart
one train at one station travels at 50mph and decreases its speed every 10 miles by 10%
second train at opposite station travels at 25mph and increases its speed every 10 miles by 10%.
the train tracks separating the stations is a sinusoidal wave with amplitude of 5 miles and goes through 3 periods between the two stations.
There are intermittant clouds in the sky resulting in intervals of 30 mins brightness and 45 mins darkness. The trains are solar powered so they cannot run during those darkness periods and assume they run at their speeds instantly when there is brightness (meaning dont account for the time to accelerate to their speed). How long will it take for the trains to reach each other?

 

[oreoeater82]

if i need to know this for the QR section i'm in trouble.... there is no way i'm gonna attempt this cause i take the DAT on Saturday... i'd just be wasting my time!

 

[vsun]

ya i was just joking about that problem
good luck on saturday