This Common Core Math lesson allows students to learn and practice solving for the unknown partner/missing addend. Students work with a partner using their Fallin’ Jelly Bean mat to solve for the missing addend/unknown partner. Students use jellybeans. Using their missing addend cards, they determine the sum and place the total amount of jellybeans at the top of the hill. Students act out the known part/addend “falls” down one side of the mountain discovering the missing addend/unknown part at the top of the hill. Students complete the data sheet to match their Fallin’ Jelly Bean Mat. Early finishers can complete the addition data sheet.