problem solving [broken calculator] [1] [5] [add subtract]

1 = 2 = 3 = 4 = 5 = 6 = 7 = 8 = 9 = 10 = 11 = 12 = 13 = 14 = 15 = 16 = 17 = 18 = 19 = 20 =

Use the keys on this broken calculator to make the totals from 1 to 20. Try to use just two of the functions + and --. Record your answers in the table on the right hand side. To restart the activity just refresh the page.