28. Выполни умножение: 323 × 3; 107 × 5; 145 × 4; 107 × 2.

323 × 3 = 300 × 3 + 20 × 3 + 3 × 3 = 900 + 60 + 9 = 969.

107 × 5 = 100 × 5 + 0 × 5 + 7 × 5 = 500 + 35 = 535.

145 × 4 = 100 × 4 + 40 × 4 + 5 × 4 = 400 + 160 + 20 = 580.

107 × 2 = 100 × 2 + 0 × 2 + 7 × 2 = 200 + 14 = 214.