SOLUTION: A car's rate is 50 kph. A truck's rate is 40 kph. If the car starts later by 5 km in comparison's to the truck's, how many minutes before the car reaches the truck? Is it 30 min

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Question 1039115: A car's rate is 50 kph. A truck's rate is 40 kph. If the car starts later by 5 km in comparison's to the truck's, how many minutes before the car reaches the truck?
Is it 30 minutes? But how did you arrive with this answer?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Start a stopwatch when the car leaves.
Let +t+ = the time on the stopwatch in
hrs when the car catches up with the truck
Let +d+ = the distance in km the car travels
until it catches up with the truck
---------------------------------------
Equation for the car:
(1) +d+=+50t+
Equation for the truck:
(2) +d+-+5+=+40t+
--------------------
Substitute (1) into (2)
(2) +50t+-+5+=+40t+
(2) +10t+=+5+
(2) +t+=+1%2F2+
------------------
The car catches up with the truck 1/2 after
the CAR leaves.This is an important point.
---------------
If you wanted to know the time in hrs to catch the truck
after the truck leaves, you must add in the truck's time
to travel 5 km
+5+=+40t%5B1%5D+
+t%5B1%5D+=+1%2F8+
+t+%2B+t%5B1%5D+=+4%2F8+%2B+1%2F8+=+5%2F8+
The car catches the truck 5/8 hr after the TRUCK leaves.
This isn't what was wanted, so you don't care about it.