SOLUTION: A car traveled the first 100 kilometers of a trip at one speed and the last 135 kilometers at an average of 5 kilometers per hour less. If the entire trip took 5 hours, what was th
Question 1186015: A car traveled the first 100 kilometers of a trip at one speed and the last 135 kilometers at an average of 5 kilometers per hour less. If the entire trip took 5 hours, what was the average speed of the car for the first part of the trip? (Applying quadratic equations) Found 2 solutions by josgarithmetic, ikleyn:Answer by josgarithmetic(39617) (Show Source):
SPEED TIME DISTANCE
first r 100/r 100
last r-5 135/(r-5) 135
SUM 5
In simplifying and solving this equation, a quadratic equation will occur.
-------------------------------THIS BELOW IS WRONG--------------------------------
----------------------------------------------------------------------------------
SPEED TIME DISTANCE
first r 100/r 100
last r-135 135/(r-135) 135
SUM 5
In simplifying and solving this equation, a quadratic equation will occur.
The "time" equation is
+ = 5 hours. (1)
The solution can be easily guessed MENTALLY: r = 50 km/h.
CHECK. + = 2 + 3 = 5 hours. ! Correct !
Solved.
-------------
Alternatively, you can reduce equation (1) to the standard quadratic equation form
and solve it formally EITHER using the quadratic formula OR by factoring.
/////////////////
Keep in mind that the setup equation is written INCORRECTLY in the post by @josgarithmetic.
(