Tyler's Family rented 15 DVDs last month. Of the 15 DVDs, 1/5 were documentaries. How many of the movies were documentarise?

To find the number of documentaries, you need to multiply the total number of DVDs rented by the fraction that represents the portion that were documentaries: 15 DVDs * 1/5 documentaries/DVD = <<15*1/5=3>>3 documentaries. Answer: \boxed{3}.