One sum per page, from 1-20 in a single Excel Sheet. Select one and < Print > < Selection > will print one page; < Print > < worksheet > will print all 20. The student may need to make a vertical chart of all possible pairs for reference. E.g., for 7: 0+7, 1+6, 2+5, 3+4, 4+3 5+2 6+1, 7+0. Each time you reopen the page the random numbers are re-generated, allowing for you to create different pages to avoid copying. However, that results in different numbers of p