Find the average speed of the boat if it sailed 7 hours at 23 km / h and 3 hours at 21 km / h.

First, we need to take and find how far the boat has traveled on each of the sections of the path. To do this, we take and multiply the travel time by the speed of the boat:

7 * 23 = 161 kilometers the boat sailed in 7 hours.

The boat sailed 3 * 21 = 63 kilometers in 3 hours.

Now we are looking for the total distance, that is, we find the sum:

161 + 63 = 224 kilometers.

Now we take and divide the distance by the travel time, that is, 10 hours, so we will find the average speed of the boat:

224: 10 = 22.4 kilometers average boat speed.

Answer: 22.4 km / h.