SOLUTION: Vinnie drives his car 120 miles and has a mean of a certain speed. If the mean speed had been 6 mph more, he could have traveled 136 miles in the same length of time. What was his

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Question 1029799: Vinnie drives his car 120 miles and has a mean of a certain speed. If the mean speed had been 6 mph more, he could have traveled 136 miles in the same length of time. What was his mean speed?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +d+ = distance in miles
Let +r+ = average rate in mi/hr
Let +t+ = time in hrs
+d+=+r%2At+
+t+=+d%2Fr+
+t+=+120+%2F+r+
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also given:
+t=+136+%2F+%28+r+%2B+6+%29+
------------------
The times were the same, so
+120%2Fr+=+136%2F%28+r+%2B+6+%29+
Multiply both sides by +r%2A%28+r+%2B+6+%29+
+120%2A%28+r+%2B+6+%29+=+136r+
+120r+%2B+720+=+136r+
+16r+=+720+
+r+=+45+
The mean speed was 45 mi/hr
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check:
+t+=+120+%2F+r+
+t+=+120+%2F+45+
+t+=+2.667+ hrs
and
+t=+136+%2F+%28+r+%2B+6+%29+
+t=+136+%2F+%28+45+%2B+6+%29+
+t+=+136+%2F+51+
+t+=+2.667+ hrs
OK