Найдите значение выражения: а) (-1 целая 1/9)*(1 целая 3/5-1/4)+2,5 б) -3

Найдём значение выражения:

1. (-1 1/9) * (1 3/5 - 1/4) + 2,5 = 1.

1) 1 3/5 - 1/4 = 1 + 12/20 - 5/20 = 1 + 7/20 = 1 7/20;

2) -1 1/9 * 1 7/20 = -10/9 * 27/20 = (-10 * 9 * 3)/(9 * 2 * 10) = -3/2 = -1,5;

3) -1,5 + 2,5 = 1.

2. -3 3/15 * 1 7/8 = -(3 * 15 + 3)/15 * (8 + 7)/8 = -48/15 * 15/8 = (-6 * 8 * 15)/(15 * 8) = -6.

3. (3 1/6 - 2 7/15) : (-1 2/5) = -1/2.

1) 3 1/6 - 2 7/15 = 3 - 2 + 1/6 - 7/15 = 1 + 10/60 - (7 * 4)/60 = 1 + 10/60 - 28/60 = 1 + (10 - 28)/60 = 1 - 18/60 = 1 - 3/10 = 10/10 - 3/10 = 7/10;

2) 7/10 : (-1 2/5) = 7/10 : (-7/5) = -(7/10 * 5/7) = -((7 * 5)/(5 * 2 * 7)) = -1/2.