SOLUTION: Two cities X and Y are connected by a highway. A car leaves city X at 12:00 noon at the constant speed of 55 mi/hr, traveling on the highway towards city Y. Twenty minutes later an

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: Two cities X and Y are connected by a highway. A car leaves city X at 12:00 noon at the constant speed of 55 mi/hr, traveling on the highway towards city Y. Twenty minutes later an      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


   



Question 945811: Two cities X and Y are connected by a highway. A car leaves city X at 12:00 noon at the constant speed of 55 mi/hr, traveling on the highway towards city Y. Twenty minutes later another car leaves city X traveling towards city Y on the same highway as the first car, at the constant speed of 60 mi/hr. At what time will the second car reach the first car? (The lengths of the cars are disregarded.)
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
What is 1st car's head start?
+d%5B1%5D+=+55%2A%28+20%2F60+%29+
+d%5B1%5D+=+18.333+ mi
-----------------------
Start a stop watch when 2nd car
leaves. Let +t+ = time in hrs
on stop watch when 2nd car
catches the 1st car
Let +d+ = distance in miles 2nd
car travels until it catches 1st car
------------------------------
1st car's equation:
(1) +d+-+18.333+=+55t+
2nd car's equation:
(2) +d+=+60t+
----------------
Substitute (2) into (1)
(1) +60t+-+18.333+=+55t+
(1) +5t+=+18.333+
(1) +t+=+3.667+
------------------
Add 20 minutes to this time
( converted to hrs )
+3.667+%2B+.333+=+4+
2nd car reaches 1st car at:
12:00 noon + 4 hrs = 4:00 PM
-----------------------------
check:
(2) +d+=+60t+
(2) +d+=+60%2A3.667+
(2) +d+=+220+
and
(1) +d+-+18.333+=+55t+
(1) +d+-+18.333+=+55%2A3.667+
(1) +d+=+201.667+%2B+18.333+
(1) +d+=+220+
OK