This Fluency Activity is a part of the Lesson 11, Unit 4, Grade 1. By reviewing the relationship between addition and subtraction within 10, students approach today's problem types with familiar strategies. In today's lesson, students make the connection that differences for multiples of 10 such as 40 - 30 can be viewed as 4 tens - 3 tens. Write a number bond for a number between 0 and 10 with a missing part. Students write an addition and a subtraction sentence to find the missing part and solve.