This Fluency Activity is a part of the Lesson 15, Unit 4, Grade 1. This fluency activity builds a student's ability to add and subtract within 10 while reinforcing the relationship between addition and subtraction. Write a number bond for a number between 0 and 10, with a missing part or whole. Students write an addition and a subtraction sentence with a box for the missing number in each equation. They then solve for the missing number.