Word problem, Dept.

The following word problem appeared in a traditional algebra textbook around. I will identify the book later. Right now I want to know your opinion of the problem, good or bad. If you dislike it, please specify why. Same if you like it.

Thanks.

Two boys are camped at a spot where a river enters a big lake.  One boy is injured so severely that every minute counts.  His companion can use an outboard motorboat to get a doctor by going 3 miles down the lake and back, or by going 3 miles up the river and back.  Show that even though the boy does not know the speed of either the boat or the current, he should choose the lake.