How many kilometers does a boat cover in a quarter of an hour if it covers 20 km in an hour?

Brief notation of the problem condition:
1 hour – 20 km;
Time – 1/4 hour;
Distance =?
Decision:
There are four quarters of an hour in one hour: 1 hour = 4/4 hours = (4 * 1/4) hours.
If a boat travels 20 km in an hour, then to find how many kilometers a boat travels in a quarter of an hour, you need to divide the distance that it covers in an hour by 4. Then:
20: 4 = 7.5 (km.)
Answer: 7.5 km.