This Instructional Activity is a part of the Lesson 11, Unit 5, Grade 7. Begin this example by posing the questions in the text to the class: If there are more than people in a group, will at least two people have the same birth month? Why? There are 12 months, and there are more than people in the group. So, even if the first 12 people in the group have different birth months, the 13th member will have to share with someone else. What is the probability this will occur?