SOLUTION: Alejandra went on a 40 mile trip to a soccer game. On the way back, due to road construction she had to drive 20 miles per hour slower. This made the trip take 1 hour longer. How f

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: Alejandra went on a 40 mile trip to a soccer game. On the way back, due to road construction she had to drive 20 miles per hour slower. This made the trip take 1 hour longer. How f      Log On


   

Question 1029726: Alejandra went on a 40 mile trip to a soccer game. On the way back, due to road construction she had to drive 20 miles per hour slower. This made the trip take 1 hour longer. How fast did she drive to the soccer game?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
R%2At=D
.
.
Trip to game,
1.R%2At=40
.
.
Trip back from game,
2.%28R-20%29%2A%28t%2B1%29=40
From 1,
R=40%2Ft
Substituting into 2,
%2840%2Ft-20%29%28t%2B1%29=40
Multiply both sides by t,
%2840-20t%29%28t%2B1%29=40t
40t%2B40-20t%5E2-20t=40t
-20t%5E2-60t%2B40=0
t%5E2%2B3t%2B2=0
%28t%2B3%29%28t-1%29=0
Only positive time solutions make sense,
t-1=0
t=1
So then,
R=40%2F1
R=40
She drove at 40 mph.