Завдання 401 - 500 » 447

Обчисліть: 1) (1/2 + 1/3) ∙ 3/10 = (3/6 + 2/6) ∙ 3/10 = 5/6 ∙ 3/10 = (1 • 1)/(2 • 2) = 1/4; 2) (1/2 – 1/3) ∙ 12/13 = (3/6 – 2/6) ∙ 12/13 = 1/6 ∙ 3/10 = (1 • 1)/(2 • 10) = 1/20; 3) 8/15 ∙ (1/2 – 1/4) = 8/15 ∙ (2/4 – 1/4) = 8/15 ∙ 1/4 = (2 • 1)/(15 • 1) = 2/15; 4) (5/6 – 1/4) ∙ 9/14 = (10/12 – 3/12) ∙ 9/14 = 7/12 ∙ 9/14 = (1 • 9)/(12 • 2) = 9/24; 5) (2/3 + 1/12) ∙ 8/9 = (8/12 + 1/12) ∙ 8/9 = 9/12 ∙ 8/9 = (1 • 2)/(3 • 1) = 2/3; 6) 20/21 ∙ (4/5 – 1/10) = 20/21 ∙ (8/10 – 1/10) = 20/21 ∙ 7/10 = (2 • 1)/(3 • 1) = 2/3.