Averaging Speeds of Individual LapsDate: 12/12/2003 at 03:00:45 From: Jaggu Subject: Average Speed A driver drives four laps around a track at 10, 20, 30, and 60 km per hour. What is his average speed? Date: 12/12/2003 at 08:09:00 From: Doctor Luis Subject: Re: Average Speed Hi Jaggu, The average speed is defined as average speed = total distance / total time Suppose the length of the track is L km. Then the total distance is total distance = 4*L km But how do we find the total time? If he drives L km at a speed of 10 km per hour, then the trip takes time = distance / speed = (L km) / (10 km/hr) = (L/10) hours So the total time is total time = ((L/10) + (L/20) + (L/30) + (L/60)) hours When you divide those two quantities, the unknown track length L should cancel out, leaving you with the average speed. I hope this helped! Let us know if you have any more questions. - Doctor Luis, The Math Forum http://mathforum.org/dr.math/ |
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