Oblicz sprytnie : a] 342 * 4 = 67 * 6 = b] 47 * 5 = 137 * 50 = c] 270 :5 = 3900 : 50

324 * 4 = 300 *4 + 20 * 4 + 4 * 4 = 1200 + 80 + 16 = 1296 67 * 6 = 60 *6 + 7 * 6 = 360 + 42 = 402 b 47 * 5 = 40 *5 + 7 * 5 = 200 + 35 = 235 137 * 50 = 100 * 50 + 30 * 50 + 7 * 50 = 6850 c 270 : 5 = 200 : 5 + 70 : 5 = 40 + 14 = 54 3900 : 50 = 3000 : 50 + 900 : 50 = 60 + 18 = 78