SOLUTION: Please help me solve the following problem: Thalia drove her car 180 miles north at a constant rate and returned 180 miles south traveling 15 mph slower than she did when she tr

Question 319688: Please help me solve the following problem:
Thalia drove her car 180 miles north at a constant rate and returned 180 miles south traveling 15 mph slower than she did when she traveled north on the same route. If the return trip took her an hour longer, how fast was she traveling northbound?

Answer by checkley77(12844) (Show Source): You can put this solution on YOUR website!
D=RT
180=RT NORTH TRIP OR R=180/T
180=(R-15)(T+1) SOUTH TRIP
180=[(180/T)-15](T+1)
180=180-15T+180/T-15
0=-15T+180/T-15
(-15T^2+180-15T)/T=0
-15T^2-15T+180=0
15T^2+15T-180=0
15(T^2+T-12=0
15(T+4)(T-3)=0
T-3=0
T=3 HOURS FOR THE TRIP NORTH
180=R*3
3R=180
R=180/3
R=60 MPH. FOR THE NORTH TRIP.
180=(60-15)(3+1)
180=45*4
180=180

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