Problema Solution
A boat travels 60 miles to an island and the same 60 miles coming back. Changes in the wind and tide made the average speed on the return trip 3 mph slower than the speed on the way out. If the total time of the trip took 9 hours, find the speed going to the island and the speed on the return trip
Answer provided by our tutors
Let
d = 60 mi the distance to the island
v = the speed going to the island, v>0
v-3 = the speed on the return trip (changes in the wind and tide made the average speed on the return trip 3 mph slower than the speed on the way out), v-3>0 that is v>3
t = 9 hr the total time of the trip
Since speed = distance/time follows time = distance/speed:
d/v + d/(v-3) = t
60/v + 60/(v - 3) = 9
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click here to see the solution for v
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v = 15 mph
v can not be 4/3 since 4/3 < 3.
The speed going to the island was 15 mph.
The speed returning from the island was 15 - 3 = 12 mph.