SOLUTION: Mary left the hardware store and traveled toward her cabin on the lake at an average speed of 52 mph. Stefan left one hour later and traveled in the same direction but with an aver

Algebra ->  Equations -> SOLUTION: Mary left the hardware store and traveled toward her cabin on the lake at an average speed of 52 mph. Stefan left one hour later and traveled in the same direction but with an aver      Log On


   



Question 1023427: Mary left the hardware store and traveled toward her cabin on the lake at an average speed of 52 mph. Stefan left one hour later and traveled in the same direction but with an average speed of 65 mph. How long did Mary travel before Stefan caught up?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
What is Mary's head start in miles?
+d%5B1%5D+=+52%2A1+
+d%5B1%5D+=+52+ mi
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Start a stopwatch when Stefan leaves.
Let +t+ = the time in hrs on the stopwatch when
he catches up with Mary.
Let +d+ = the distance in miles that Stefan
has traveled until he catches up with Mary
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Mary's equation:
(1) +d+-+52+=+52t+
Stefan's equation:
(2) +d+=+65t+
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Plug (2) into (1)
(1) +65t+-+52+=+52t+
(1) +13t+=+52+
(1) +t+=+4+
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(2) +d+=+65%2A4+
(2) +d+=+260+
Mary traveled 260 miles before Stefan caught up
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( note that this 260 mi INCLUDES the 52 mi head start she had,
so she traveled another +260+-+52+=+208+ mi AFTER
Stefan left )
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check answer:
(1) +d+-+52+=+52t+
(1) +d+-+52+=+52%2A4+
(1) +d+=+208+%2B+52+
(1) +d+=+260+
OK