SOLUTION: i sailed west to hawaii against the wind at a speed 12 knots/hour. when i returned, i sailed the same route with a wind at a speed of 18 knots/hour. what was my average speed for t

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Question 381937: i sailed west to hawaii against the wind at a speed 12 knots/hour. when i returned, i sailed the same route with a wind at a speed of 18 knots/hour. what was my average speed for the entire trip?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
i sailed west to Hawaii against the wind at a speed 12 knots/hour.
when i returned, i sailed the same route with a wind at a speed of 18 knots/hour.
what was my average speed for the entire trip?
:
Let a = average speed for the entire trip
:
Let d = the one way distance
:
Write a time equation: time = dist/speed
:
to time + return time = total time
d%2F12 + d%2F18 = %282d%29%2Fa
:
We don't need d, divide thru by d and you have
1%2F12 + 1%2F18 = 2%2Fa
Multiply by 36a to clear the denominators, results
3a + 2a = 36(2)
:
5a = 72
a = 72%2F5
a = 14.4 knot/hr is the av for the entire trip