SOLUTION: The 42km drive from Oakdale to Ridgemont usually takes 28 min. Because highway construction requires a reduced speed limit, the trip now takes 14 min longer. Find the reduced speed

Question 118717: The 42km drive from Oakdale to Ridgemont usually takes 28 min. Because highway construction requires a reduced speed limit, the trip now takes 14 min longer. Find the reduced speed limit in km/h.
Found 2 solutions by m.hansen, MathLover1:
Answer by m.hansen(16) (Show Source): You can put this solution on YOUR website!
distance = 42km
time = 28min + 14min = 42min
speed =
= 1 km/min
In more usual units of km/hr.
= .7 hr
= 60 km/hr
Answer by MathLover1(20849) (Show Source): You can put this solution on YOUR website!
note that "" is the variable for speed, that "" is the variable for distance, and that "" is the variable for time
the drive from Oakdale to Ridgemont is your distance
the time
the speed is:

Then usual speed is:
�.divide both sides by

��..since is , we will have

��..

��..simplify

��..

let a reduced speed limit be

distance remain same

since the trip now takes , we can write the time as

which is , or

then

��. is , then we will have

��.

��. a reduced speed limit

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