SOLUTION: Two cars each complete a journey of 120 km. The first car is driven at an average speed of x km/h. The second car is driven at an average speed 3 km/h faster than the first car.

Question 934701: Two cars each complete a journey of 120 km.
The first car is driven at an average speed of x km/h.
The second car is driven at an average speed 3 km/h faster than the first car.
The first car takes 6 minutes longer to complete the journey.
Write down an equation in x and show that it simplifies to x2 + 3x � 3600 = 0.
Answer by TimothyLamb(4379) (Show Source): You can put this solution on YOUR website!
x = speed of first car
y = speed of second car
t = time of second car
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y = x + 3
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s = d/t
t = d/s
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time of first car:
t + 6/60 = 120/x
t = 120/x - 6/60
---
time of second car:
t = 120/y
t = 120/(x + 3)
---
equate times:
120/x - 6/60 = 120/(x + 3)
120/x - 120/(x + 3) = 6/60
120(x + 3)/x(x + 3) - 120x/x(x + 3) = 6/60
120(x + 3) - 120x = (6/60)x(x + 3)
120x + 360 - 120x = (6/60)xx + 3*(6/60)x
360 = (6/60)xx + 3*(6/60)x
(6/60)xx + 3*(6/60)x - 360 = 0
( (6/60)xx + 3*(6/60)x - 360 = 0 )/6
(1/60)xx + 3*(1/60)x - 60 = 0
( (1/60)xx + 3*(1/60)x - 60 = 0 )*60
(1/1)xx + 3*(1/1)x - 60*60 = 0
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answer:
xx + 3x - 3600 = 0
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