Вправи 101 - 200 » 103

Обчисліть зручним способом. а) 3/14 + 1/28 + 3/25 + 1/14 + 2/25 + 3/28 + 1/10 + 3/10 = (3/14 + 1/14) + (1/28 + 3/28) + (3/25 + 2/25) + 1/10 + 3/10 = 4/14 + 4/28 + 1/5 + 4/10 = (8/28 + 4/28) + (2/10 + 4/10) = 12/28 + 6/10 = 3/7 + 3/5 = 15/35 + 21/35 = 36/35 = 11/35. б) 5/12 + 3/8 - 1/12 + 7/16 - 3/16 - 1/8 + 21/24 - 17/24 = (5/12 - 1/12) + (3/8 - 1/8) + (7/16 - 3/16) + (21/24 - 17/24) = 4/12 + 2/8 + 4/16 + 4/24 = 1/3 + 1/4 + 1/4 + 1/5 = 5/15 + 3/15 + 1/2 = 1/5 + 1/2 = 2/10 + 5/10 = 7/10. в) 2/15 + 24/25 + 7/20 + 13/15 - 4/25 + 8/9 - 3/20 + 1/9 = (24/25 - 4/25) + (2/15 + 13/15) + (7/20 - 3/20) + (8/9 + 1/9) = 20/25 + 15/15 + 4/20 + 9/9 = 2 + 4/5 + 1/5 = 3.