А)4/15:2/5 б)5/6:30 в)20:2 1/2 г)2 1/4:3 д)15:12

Вычислим значения выражений:

А) 4/15 : 2/5 = 4/15 * 5/2 = 5/15 * 4/2 = 1/3 * 4/2 = 1/3 * 2 = 2/3; 

б) 5/6 : 30 = 5/6 * 1/30 = 5/30 * 1/6 = 1/6 * 1/6 = 1/36; 

в) 20 : 2 1/2 = 20 : (2 * 2 + 1)/2 = 20 : (4 + 1)/2 = 20 : 5/2 = 20 * 2/5 = 20/5 * 2 = 4 * 2 = 8; 

г) 2 1/4 : 3 = (2 * 4 + 1)/4 : 3 = (8 + 1)/4  : 3 = 9/4 : 3 = 9/4 * 1/3 = 9/3 * 1/4 = 3 * 1/4 = 3/4; 

д) 15 : 12 = 15/12 = (3  * 5)/(3 * 4) = (1 * 5)/(1 * 4) = 5/4 = 1 1/4.