Вычислить сумму. 11/30+7/12, 1/6+1/10+1/15, 5/12+2/9+1/18, 1/2+1/3+1/9

Чтобы отыскать сумму приведем дроби к общему знаменателю:

1) 11/30 + 7/12 = (11 * 2)/(30 * 2) + (7 * 5)/(12 * 5) = 22/60 + 35/60 = (22 + 35)/60 = 57/60;

2) 1/6 + 1/10 + 1/15 = (1 * 5)/(6 * 5) + (1 * 3)/(10 * 3) + (1 * 2)/(15 * 2) = 5/30 + 3/30 + 2/30 = (5 + 3 + 2)/30 = 10/30 = 10/(3 * 10) = 1/3;

3) 5/12 + 2/9 + 1/18 = (5 * 3)/(12 * 3) + (2 * 4)/(9 * 4) + (1 * 2)/(18 * 2) = 15/36 + 8/36 + 2/36 = (15 + 8 + 2)/36 = 25/36;

4) 1/2 + 1/3 + 1/9 = (1 * 9)/(2 * 9) + (1 * 6)/(3 * 6) + (1 * 2)/(9 * 2) = 9/18 + 6/18 + 2/18 = (9 + 6 + 2)/18 = 17/18.