<PRE><B>Question 628312</B>
An automobile car traveled 200 miles and at same time 
a truck can travel 150 miles .
If the automobile travels at the average speed of 15 miles per hour faster
 than the truck then . 
Find their average rate?
:
Let s = speed of the truck
then
(s+15) = speed of the car
;
Write a time equation: time = dist/speed
:
truck time = car time
{{{150/s}}} = {{{200/((s+15))}}}
Cross multiply
150(s+15) = 200s
150s = 2250 = 200s
2250 = 200s - 150s
2250 = 50s
s = 2250/50
s = 45 mph is the speed of the truck
then
45 + 15 = 60 mph is the speed of the car
:
:
Confirm this by finding the time of each, they should be equal
150/45 =  3.33 hrs
200/60 = 3.33 hrs</PRE>