Recent content by ethereal45

  1. E

    Simple Diff EQ - Modeling the salt concentration of a pond

    Here is my work, I have no clue what I'm doing wrong but this is definitely not the right answer: http://alex.fangsoft.net/mathwork.pdf
  2. E

    Simple Diff EQ - Modeling the salt concentration of a pond

    so I get -250000/150 ln (abs(7.5-150y/250,000) +c = t So solve for y ? One of my friends did this in maple and I'm just not getting an equation for y that agrees with him :(
  3. E

    Simple Diff EQ - Modeling the salt concentration of a pond

    yeah it's been a while since I've done integrals, I just made a u-substitution and found out what it should be!
  4. E

    Simple Diff EQ - Modeling the salt concentration of a pond

    Okay, so... dy/(7.5-150y/250000) = dt I understand that concept, but I have zero idea how to evaluate the resulting integral, on the left hand side anyways.
  5. E

    Simple Diff EQ - Modeling the salt concentration of a pond

    Okay I understand what I've done so far, but for some reason I'm having a lot of trouble solving it...I understand to do with my initial value after I solve...but what are my first few algebra moves?
  6. E

    Simple Diff EQ - Modeling the salt concentration of a pond

    Okay, so I know ds/dt = salt in - salt out. As for Salt In: I know I have 50gal/hr x .15lb / gal = 7.5 lb / hour For Salt Out: I have 150 gal/hr x the concentration at that given time. Do I represent that as 150 x (25,000lb + 7.5 t)/250,000 where 25,000 is the starting amount of salt...
  7. E

    Simple Diff EQ - Modeling the salt concentration of a pond

    Homework Statement The problem can be found here: http://alex.fangsoft.net/math.pdf I have completed Task #2, it is Task #1 that I am very lost on. Our teacher has really thrown us head first into the water with this one, I am very unfamiliar with differential equations and their...