Answer:
2 hours
Step-by-step explanation:
The relation between time, speed, and distance is ...
time = distance/speed
For a kayak speed of k miles per hour in still water, the speed upstream is (k-2) and the speed downstream is (k+2). Over the distances given, the times are the same, so we can write ...
10/(k-2) = 14/(k+2)
Multiplying by (k+2)(k-2) gives ...
10(k+2) = 14(k -2)
10k +20 = 14k -28 . . . . . eliminate parentheses
48 = 4k . . . . . . . . . . . . . . add 28-10k
12 = k
Then the time for 28 miles downstream is ...
time = 28 / (12 +2) = 2 . . . . hours
It will take the person 2 hours to kayak 28 miles downstream.
