Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Story problems for Algebra II/Trig review test

  1. Aug 11, 2010 #1
    1. The problem statement, all variables and given/known data
    at noon a train leaves B heading East at 90 mi/h to C which is 450 miles away
    at 12:15 pm a train leaves C heading West to B at 100 mi/h. When will they pass each other?


    2. Relevant equations t=0 when train leaves B and train leaving C is ) at t=15min



    3. The attempt at a solution Graph hours on the x axis and miles on the y axis, but how do you graph the train leaving C? I don't see how the lines intersect. Where do I go to get basic information on these types of problems?
     
  2. jcsd
  3. Aug 12, 2010 #2
    You don't need to graph anything.

    Let t be the number of hours since noon that have elapsed.
    Can you write down an expression in terms of t for how far apart the trains are?
    (hint: they start 450 miles apart and one train leaves earlier)

    Once you have done that, they will pass each other at a time t that makes your expression equal zero (because then they will be zero miles apart!)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook