Description: First, a definition: A unit fraction is a fraction with a numerator of 1. Then the questions: Find the longest string of different unit fractions with the denominator having an upper bound of 25. If you are adventurous make the upper bound 50 or even 100. Explain how you did it. This is a question where all (or at least some) of the students can work together. The answers for 50 and for 100 are not known for certain.