Make Students Write their own Formulas!! This activity consists of 5 simple worksheets in 1 workbook (Excel) where students have to write their own formulas with no directions. After I have explained simple formulas and basic functions to students, I use this as a reinforcement activity. At the beginning of each period, I put up one worksheet on my Smart Board and have students supply formulas to solve the problem. GREAT CLASS STARTER! Problem topics include: Family Camping Trip, Let's Go