Question 1086473: 1)Lisa drove 60 miles, then increased her speed by 15 miles per hour for 135 miles. If the second part of the drive took 1 hour longer than the first part, find her average speed.
What I have so far: 240/(s-20) -60/s the whole eq multiplied by s(s-20)
Found 2 solutions by jorel1380, MathTherapy:
Answer by jorel1380(3719)   (Show Source):
You can put this solution on YOUR website! Let n-15 be Lisa's first speed, and n be her second speed. Then:
60/(n-15) +1=135/n
60n+n²-15n=135(n-15)
n²-90n+2025=0
(n-45)²=0
n=45
n-15=30
60/30=2
135/45=
135+60 miles/2+3 hours=39 mph avg
☺☺☺☺
Answer by MathTherapy(10555)  (Show Source):
You can put this solution on YOUR website! 1)Lisa drove 60 miles, then increased her speed by 15 miles per hour for 135 miles. If the second part of the drive took 1 hour longer than the first part, find her average speed.
What I have so far: 240/(s-20) -60/s the whole eq multiplied by s(s-20)
1st, I think the numbers you have, so far, have nothing to do with this problem. I think the numbers you have, so far, have to do with: Travel_Word_Problems/1086474:
The answer to this problem (# 1086473): 
IGNORE anyone who says otherwise!
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