A cyclist bikes x distance at 10 miles per hour and returns over the same path at 8 miles per hour. What is the cyclist’s average rate for the round trip in miles per hour?
2007-02-26 04:14:57 · 3 answers · asked by MisterMeToo 1 in Science & Mathematics ➔ Mathematics
Let the distance one way be x.
Then it takes x / 10 hours to get there, and x / 8 hours to get back.
All told, it takes x / 10 + x / 8 = 4x / 40 + 5x / 40 = 9x / 40 hours.
The total distance travelled is, of course, 2x.
Therefore, the average speed is total distance / total time:
2x / (9x / 40) = 2x * (40 / 9x) = 80/9 = 8.8888... mph.
2007-02-26 04:48:48 · answer #1 · answered by Phred 3 · 0⤊ 0⤋
time taken to travel = 10/x + 8/x
= 12/x
total distance travelled = 2x
average rate = total distance travelled/total time taken
= 2x/(12/x)
=(x^2)/6 miles per hour
2007-02-26 12:26:52 · answer #2 · answered by lwyenin 2 · 0⤊ 0⤋
**** you need the formula?
2007-02-26 12:29:12 · answer #3 · answered by The Dude 2 · 0⤊ 0⤋