Частина 2 — Відповіді: Стр.19 (4)

4. Попрацюй за варіантами. Обчисли значення виразів.

660 + 200 = (600 + 200) + 60 = 860;

660 + 20 = 600 + (60 + 20) = 680;

660 – 200 = (600 – 200) + 60 = 460;

660 – 20 = 600 + (60 – 20) = 640;

350 + 300 = (300 + 300) + 50 = 650;

350 + 30 = 300 + (50 + 30) = 380;

870 – 500 = (800 – 500) + 70 = 370;

870 – 50 = 800 + (70 – 50) = 820;

570 + 200 = (500 + 200) + 70 = 770;

570 – 200 = (500 – 200) + 70 = 370;

570 + 20 = 500 + (70 + 20) = 590;

570 – 20 = 500 + (70 – 20) = 550;

750 + 200 = (700 + 200) + 50 = 950;

750 + 20 = 700 + (50 + 20) = 770;

750 – 200 = (700 – 200) + 50 = 550;

750 – 20 = 700 + (50 – 20) = 730;

460 + 300 = (400 + 300) + 60 = 760;

460 + 30 = 400 + (60 + 30) = 490;

460 – 300 = (400 – 300) + 60 = 160;

460 – 30 = 400 + (60 – 30) = 430;

450 + 200 = 650;

450 + 20 = 470;

860 – 700 = 160;

740 – 20 = 720.