An old chestnut
which reappeared recently in Parade magazine
goes as follows:
Two riverboats starting from opposite banks of a river start traveling toward each other at different, constant speeds. The first pass each other 700 yards from one bank. They continue, and each boat turns around instantaneously when it reaches the opposite bank. They pass each other again 300 yards from the other bank.
Ignore the physical problems with instantaneous acceleration in this problem.
1. How wide is the river?
2. What is it that makes this particular puzzle so baffling for many people?