【Question 7】
A boat is sailing in a river, traveling downstream at a speed of 15 kilometers per hour. It is known that the boat travels the same distance in 4 hours downstream as it does in 5 hours upstream. What is the speed of the current in kilometers per hour?
【Analysis and Solution】
Travel problem, boat in running water.
Downstream speed is 15 km/h;
Upstream speed is $15 \times 4 \div 5=12$ km/h;
Water speed is $(15-12) \div 2=1.5$ km/h.