You are in a speedboat on a river moving in the same direction as the current. The speedometer on the boat shows its speed is 20 km/h. However, a person on the shore measures the boat's speed as 23 km/h. How is this possible?

1 Answer
Mar 22, 2017


See explanation.


It is possible. The speedometer shows only the speed of boat, but due to the current the actual speed may be different than the indication of the speedometer.

Here the boat moves in the same direction as the current, so the speeds add up. This means that despite the speedometer shows
20 km/h the actual speed is greater (23 km/h). The speed of the current is the additional 3 km/h.

If the boat was running against the current then the speeds would have to be subtracted, so although the meter would show #20# the actual speed measured my a man on the shore would be #20-3=17#