Question 620347

<pre>60mph is 1 mile per minute.  So 6 minutes later, when the car enters,
the truck is 6 miles up the road.  The car's approach rate is 9 miles
per hour, found by subtracting their speeds 69-60.  

TIME = DISTANCE/RATE = 6/9 = 2/3 of an hour = 40 minutes.

Edwin</pre>