r 12 Alg Add Sub 3 of 8 + Automatic Zoom the columns have been added. This gives the desired answer. Practice Problems Problem 12.1 Use the addition expanded algorithm as discussed in this section to perform the following additions: (a) 23 + 44 (b) 57 + 84 (c) 324 + 78 Problem 12.2 Use base ten blocks to represent the sum 279 + 84. Problem 12.3 State the property that justifies each of the following steps. 36 + 52 (3 . 10 + 6) + (5 - 10 + 2) = 3 . 10 + [6 + (5 . 10 + 2)] 3 . 10 + [(6 + 5 .10) +2 = 3 . 10 + (5 . 10 +6) + 2] = 3 . 10 + [5 . 10 + (6 + 2)] = (3 . 10 + 5 . 10) + (6 +2) (3 +5) . 10 + (6+2) 8 . 10 + 8 88 3 Problem 12.4