А= 1/3*4+1/4*5+1/5*6
1) 1/3*4 = 4/3 = 1 1/3
2) 1/4*5 = 5/4 = 1 1/4
3) 1/5 * 6 = 6/5 = 1 1/5
4) 1 1/3 + 1 1/4 = 1 4/12 + 1 3/12 = 2 7/12
5) 2 7/12 + 1 1/5 = 2 35/60 + 1 12/60 = 3 47/60
A = 3 47/60
12 * 3 47/60 = 12* 227/60 = 227/5 = 45 2/5
ответ: 45 2/5
А= 1/3*4+1/4*5+1/5*6
1) 1/3*4 = 4/3 = 1 1/3
2) 1/4*5 = 5/4 = 1 1/4
3) 1/5 * 6 = 6/5 = 1 1/5
4) 1 1/3 + 1 1/4 = 1 4/12 + 1 3/12 = 2 7/12
5) 2 7/12 + 1 1/5 = 2 35/60 + 1 12/60 = 3 47/60
A = 3 47/60
12 * 3 47/60 = 12* 227/60 = 227/5 = 45 2/5
ответ: 45 2/5