Частина 2 — Відповіді: Стр.31 (6)

6. Попрацюй за варіантами. Обчисли значення виразів.

620 + 280 = (600 + 200) + (20 + 80) = 800 + 100 = 900;

430 + 270 = (400 + 200) + 30 + 70 = 600 + 100 = 700;

560 + 240 = (500 + 200) + (60 + 40) = 700 + 100 = 800;

280 + 120 = (200 + 100) + (80 + 20) = 300 + 100 = 400;

600 – 220 = (600 – 200) – 20 = 400 – 20 = 380;

400 – 270 = (400 – 200) – 70 = 200 – 70 = 130;

700 – 350 = (700 – 300) – 50 = 400 – 50 = 350;

300 – 110 = (300 – 100) – 10 = 200 – 10 = 190;

350 + 250 = (300 + 200) + (50 + 50) = 500 + 100 = 600;

740 + 160 = (700 + 100) + (40 + 60) = 800 + 100 = 900;

600 – 360 = (600 – 300) – 60 = 300 – 60 = 240;

500 – 280 = (500 – 200) – 80 = 300 – 80 = 220;

160 + 240 = (100 + 200) + (60 + 40) = 300 + 100 = 400;

360 + 140 = (300 + 100) + (60 + 40) = 400 + 100 = 500;

440 + 160 = (400 + 100) + (40 + 60) = 500 + 100 = 600;

230 + 270 = (200 + 200) + (30 + 70) = 400 + 100 = 500;

700 – 260 = (700 – 200) – 60 = 500 – 60 = 440;

700 – 570 = (700 – 500) – 70 = 200 – 70 = 130;

800 – 340 = (800 – 300) – 40 = 500 – 40 = 460;

600 – 550 = (600 – 500) – 50 = 100 – 50 = 50;

Склади по два вирази виду 340 + 260, 700 – 210. Знайди їх значення.

470 + 330 = (400 + 300) + (70 + 30) = 700 + 100 = 800;

240 + 560 = (200 + 500) + (40 + 60) = 700 + 100 = 800;

500 – 320 = (500 – 300) – 20 = 200 – 20 = 180;

300 – 170 = (300 – 100) – 70 = 200 – 70 = 130.