Вычислить: а) 8/9*3/4 - (5/6-1/4) б) 3/5+4/5*3/7+6/7 в) (2/5-2/7) : 2/7*2/5

г) (5/6-3/10) : (3/10+2/15)

Вычислить:

а) 8/9*3/4 - (5/6-1/4) = 1/12.

1)) (5/6 - 1/4) = (5•2) / (6•2) - (1•3) / (4•3) = 10/12 - 3/12 = 7/12;

2)) 8/9•3/4 = 2/3• 1/1 = 2/3;

{сократили, значит поделили 8 и 4 на 4; 9 и 3 на 3};

3)) 2/3 - 7/12 = (2•4) / (3•4) - 7/12 = 8/12 - 7/12 = 1/12;

б) 3/5+4/5*3/7+6/7 = 1 целая 4/5.

1)) 4/5• 3/7 = 12/35;

2)) 3/5 + 12/35 + 6/7 = (3•7) / (5•7) + 12/35 + (6•5) / (7•5) = 21/35 + 12/35 + 30/35 = 63/35 = 1 целая 28/35 = 1 целая 4/5.

{сократили 28/35 на 7}.

в) (2/5-2/7) : 2/7*2/5 = 4/25.

1)) (2/5 - 2/7) = (2•7) / (5•7) - (2•5) / (7•5) = 14/35 - 10/35 = 4/35;

2)) 4/35 : 2/7 = 4/35• 7/2 = 2/5• 1/1 = 2/5;

{сократили 4 и 2 на 2; 35 и 7 на 7};

3)) 2/5• 2/5 = 4/25;

г) (5/6-3/10) : (3/10+2/15) = 1 целая 3/13.

1)) (5/6-3/10) = (5•5) / (6•5) - (3•3) / (10•3) = 25/30 - 9/30 = 16/30;

2)) (3/10 + 2/15) = (3•3) / (10•3) + (2•2) / (15•2) = 9/30 + 4/30 = 13/30;

3)) 16/30 : 13/30 = 16/30• 30/13 = 16/13 = 1 целая 3/13;

{сократили 30 и 30 на 30}.