SOLUTION: a truck enters a highway driving 60 mph. A car enters the highway at the same place 7 minutes later and drives 71 mph in the same direction. from the time the car enters the highwa
Algebra ->
Customizable Word Problem Solvers
-> Travel
-> SOLUTION: a truck enters a highway driving 60 mph. A car enters the highway at the same place 7 minutes later and drives 71 mph in the same direction. from the time the car enters the highwa
Log On
Question 382246: a truck enters a highway driving 60 mph. A car enters the highway at the same place 7 minutes later and drives 71 mph in the same direction. from the time the car enters the highway, how long will it take the care to pass the truck?
Work:
Truck- d=60x r=60 t=x
Car- d= 71(x-7/60) r=71 t=(x-7/60)
60x=71(x-7/60)
60x=71x-497/60
60x71x= -497/60
-11x= -497/60
x= (-497/60)/-11
x= 497/660
x= 45
But i have the answer and its 38 minutes...What am i doing wrong? Found 2 solutions by jordanmariex, Alan3354:Answer by jordanmariex(1) (Show Source):
You can put this solution on YOUR website! truck: d=60x+7
r=60
t=x
The truck is left 7 minutes before the car so if you multiply the speed 60 by 7/60 minutes you get 7.
Car: d=71x
r=71
t=x
71x=60x+7
11x=7
x=7/11
x=7/11(60) (for the minutes)
x=38
You can put this solution on YOUR website! a truck enters a highway driving 60 mph. A car enters the highway at the same place 7 minutes later and drives 71 mph in the same direction. from the time the car enters the highway, how long will it take the care to pass the truck?
----------------
60 mph = 1 mile per minute so the truck is 7 miles ahead
The car gains on the truck at 11 mph (71-60)
It will take 7/11 hours to overtake the truck
= 7*60/11 minutes
=~ 38 minutes
----------------
Your solution of 45 minutes is the time starting when the truck entered the highway.
