SOLUTION: You need to pick up your older sister from college which is 436 miles away. She is able to get a ride part way home. You agree to meet her at a point where both of you travel 4 ho

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Question 545052: You need to pick up your older sister from college which is 436 miles away. She is able to get a ride part way home. You agree to meet her at a point where both of you travel 4 hours, but you are a faster driver and are going 15 mph faster than her ride. How fast are each of you driving?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let the distance your sister travels = d
Let her speed = s
Your distance is +436+-+d+
------------------------
Sister's equation:
(1) +d+=+4s+
Your equation:
(2) +436+-+d+=+4%2A%28+s+%2B+15+%29+
-------------------------
(2) +436+-+d+=+4s+%2B+60+
Substitute (1) into (2)
(2) +436+-+4s+=+4s+%2B+60+
(2) +8s+=+436+-+60+
(2) +8s+=+376+
(2) +s+=+47+
your speed is
+s+%2B+15+=+47+%2B+15+
+s+%2B+15+=+62+
Your speed is 62 mi/hr
check:
(2) +436+-+d+=+4%2A%28+s+%2B+15+%29+
(2) +436+-+d+=+4%2A%28+47+%2B+15+%29+
(2) +d+=+436+-+4%2A62+
(2) +d+=+436+-+248+
(2) +d+=+188+
and
(1) +d+=+4s+
(1) +d+=+4%2A47+
(1) +d+=+188+
OK