This Fluency Activity is a part of the Lesson 24, Unit 4, Grade 1. This fluency activity addresses Grade 1's core fluency requirement and strengthens understanding of the relationship between addition and subtraction. Repeat the activity from Lesson 21. Today, assign partners of equal ability and an appropriate range of numbers for each pair. Allow partners to choose a number for their whole and roll the die to determine one of the parts. Both students write two addition and two subtraction sentences, with a box for the missing number in each equation, and solve for the missing number.