#### Motor Daddy

**Valued Senior Member**

Pete said:A motor boat travels at 8km/hr in still water. The boat travels 5 km upstream, then back to the starting point. If the total time taken is 1hr30mins, find the speed of the current.

If a motor boat travels at 8km/hr for 90 minutes, the boat would have traveled 6km each way, for a total of 12 km in 90 minutes, which is a speed of 8km/hr.

If the boat travels for 5 kilometers each leg of the trip, then the boat would have traveled a total of 10 kilometers in 90 minutes, and that would be a speed of 6.666 km/hr.

If the boat traveled at 8km/hr in still water for 5 km each leg of the trip, then it traveled 10 kilometers at the speed of 8km/hr, and therefore traveled for 1.25 hours, not 1.5 hours.

The problem states that the boat traveled at 8km/hr in still water. If it did travel at 8km/hr then it only took 1.25 hours to travel 10 kilometers. If it traveled at 8km/hr for 90 minutes then it would have traveled 12 kilometers round trip.

Which one is it? Did the boat travel for 90 minutes at 6.666km/hr for a total distance of 10 kilometers, or did it travel at 8km/hr for 75 minutes (1.25 hours) which is a total distance traveled of 10 kilometers?