3.393. Вычислите.

Ответы: а) 17 + 30 = 47, 5 + 25 = 30, 37 + 203 = 240, 384 + 20 = 404, 127 + 23 = 150. б) 728 - 7 = 721, 80 - 5 = 75, 100 - 17 = 83, 270 - 100 = 170. в) 20 · 5 = 100, 4 · 25 = 100, 50 · 20 = 1000, 24 · 1000 = 24000. г) 26 : 2 = 13, 144 : 9 = 16, 370 : 10 = 37, 600 : 30 = 20.