Способи усних обчислень частки » 589

180 + 240 + 320 + 260 = 180 + 320 + 240 + 260 = 500 + 500 = 1000 250 + 190 – 270 – 130 = 250 + 200 – 10 – (270 + 130) = 440 – 400 = 40 980 – 140 – 380 – 260 = 980 – 380 – (140 + 260) = 600 – 400 = 200 220 • 3 : 2 = 660 : 2 = 330 840 : 3 • 2 = (600 + 240) : 3 • 2 = (200 + 80) • 2 = 400 + 160 = 560 920 : 4 • 3 = (800 + 120) : 4 • 3 = (200 + 30) • 3 = 600 + 90 = 690 + 1(1)7(1)4 239 413 _55(*)5 248 307 + 35(1)6 206 562