Answer: the speed of the current is 8 mph.
Step-by-step explanation:
Let represent the speed of the current
boat can travel 23mph in still water. This means that the total speed with which the boat travelled is (23 + x) mph.
Time = distance/speed
If it travels 248 miles with the current, it means that the time it took the boat to travel with the current is
248/(23 + x)
in the same length of time it travels 120 miles against the current. This means that the total speed with which the boat travelled is (23 - x) mph. The time it took the boat to travel against the current is
120/(23 - x)
Since the time is the same, it means that
248/(23 + x) = 120/(23 - x)
Cross multiplying, it becomes
248(23 - x) = 120(23 + x)
5704 - 248x = 2760 + 120x
120x + 248x = 5704 - 2760
368x = 2944
x = 2944/368
x = 8 mph
