Answer:
3 km/h
Explanation:
You want to know Jose's swimming speed in still water if his time with the current for 16 km is the same as his time for 8 km when swimming against the current. The current is 1 km/h.
Time
Time is related to speed and distance by ...
time = distance/speed
If s is Jose's swimming speed, then the equal times mean ...
16/(s +1) = 8/(s -1)
16s -16 = 8s +8 . . . . . . . cross multiply
8s = 24 . . . . . . . . . . . add 16 -8s
s = 3 . . . . . . . . . . divide by 8
Jose would swim 3 km/h if there were no current.
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Additional comment
This speed is on par with an average amateur's speed for a marathon swim of the same distance. That would be about 3.2 kph for 10 km, decreasing for each additional km. Here, Jose is swimming 4 hours at that rate, an equivalent distance of 12 km.
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