SOLUTION: a train pulls cargo 140 miles and then a second one pulls it another 200 miles going 5 miles faster than the first together they take 9 hours how fast are they going

Question 337886: a train pulls cargo 140 miles and then a second one pulls it another 200 miles going 5 miles faster than the first together they take 9 hours how fast are they going
Answer by checkley77(12844) (Show Source): You can put this solution on YOUR website!
D=RT
T=D/R
9=140/X+200/(X+5)
9=((140)+200*X)/X(X+5)
9=(140X+700+200X)/(X^2+5X)
9=(340X+700)/(X^2+5X) CROSS MULTIPLY.
9(X^2+5X)=340X+700=0
9X^2+45X-340X-700=0
9X^2-295X-700=0
(9X+20)(X-35)=0
X-35=0
X=35 MPH FOR THE SLOWER TRAIN.
35+5=40 MPH FOR THE FASTER TRAIN.
PROOF:
9=140/35+200/40
9=4+5
9=9
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