Завдання 1201 - 1300 » 1275

Обчисли зручним способом: 1) ( – 2/9 + 31/18 + 1/2) · 18 = – 2/9 · 18 + (55 ∙ 18)/18 + (1 ∙ 18)/2 = –4 + 55 + 9 = 60; 2) (–3/25 + 11/3 – 1) · (–7,5) = (75 ∙ 3)/(10 ∙ 25) – (75 ∙ 4)/(10 ∙ 3) + 7,5 = 0,9 – 10 + 7,5 = –1,6; 3) –12 · 13/4 + (–12) · 21/3 = –12 · (13/4 + 21/3) = –12 · 41/12 = – (12 ∙ 49)/12 = –49; 4) –21/9 · 13 + 31/9 · 13 + 13 = 13 · (–21/9 + 31/9 + 1) = 13 · 2 = 26.