This Application Problem is a part of the Lesson 19, Unit 6, Grade 1. Ben had 16 baseball cards before a card show. After the card show, he had 20 baseball cards. How many cards were added to Ben's collection? Today's problem is an add to with change unknown problem type. As Topic F, which focuses on varied problem types, approaches, begin to take note of students' strengths and weaknesses for specific problem types.