SOLUTION: Mary leaves her home driving at 60 mph. One hour later, Jim leaves his work during the same route at 70 mph. How long will it take Jim to catch Mary?

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Question 640634: Mary leaves her home driving at 60 mph. One hour later, Jim leaves his work during the same route at 70 mph. How long will it take Jim to catch Mary?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Mary has a head start of +60%2A1+=+60+ mi
Start a stopwatch when Jim leaves
Let the time on the watch = +t+ hrs when
Jim catches Mary
Let +d+ = distance that Jim travels
to catch Mary
Mary's equation:
(1) +d+-+60+=+60t+
Jim's equation:
(2) +d+=+70t+
--------------
Substitute (2) into (1)
(1) +70t+-+60+=+60t+
(1) +10t+=+60+
(1) +t+=+6+
-----------
It will take 6 hrs for Jim to catch Mary
check:
(2) +d+=+70t+
(2) +d+=+70%2A6+
(2) +d+=+420+ mi
and
(1) +d+-+60+=+60%2A6+
(1) +d+=+360+%2B+60+
(1) +d+=+420+ mi
OK