Teaching students how to divide unit fractions by whole numbers can actually be fun! Just whip out the fraction strips and let them explore.
I like to start out this unit relating the fractions to candy bars or pizzas, something that they can visualize and understand. Discuss the idea that you only have 1/2 of the candy bar so you are starting with a fraction now and no longer a whole. Then have them visualize sharing that candy bar 1/2 with other people. In this case, 5 people are sharing it. So you ask yourself, "what fraction of the candy bar will each person get after dividing the 1/2 by 5?" The answer is 1/10. Be sure to remind your students that they are always relating the fraction back to the entire whole.
After playing around with the fraction strips my students really tend to grasp the concept and begin to see the patterns. Check out my teachers pay teachers store, here, for some fun task cards and activities relating to dividing fractions!!