а) (1 3/5 + 2 1/5) : 1 9/10 + (1 7/10 - 4/3) : 3 3/7 = 2 77/720
1) 1 3/5 + 2 1/5 = 3 4/5
2) 1 7/10 = 4/3 = 17/10 - 4/3 = 51/30 - 40/30 = 11/30
3) 3 4/5 : 1 9/10 = 19/5 : 19/10 = 19/5 · 10/19 = 10/5 = 2
4) 11/30 : 3 3/7 = 11/30 : 24/7 = 11/30 · 7/24 = 77/720
5) 2 + 77/720 = 2 целых 77/720.
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б) 6 3/8 · 1 1/17 - 2 3/8 : 1 1/4 + 2/5 = 5 1/4
1) 6 3/8 · 1 1/17 = 51/8 · 18/17 = (3·9)/(4·1) = 27/4 = 6 3/4
2) 2 3/8 : 1 1/4 = 19/8 : 5/4 = 19/8 · 4/5 = (19·1)/(2·5) = 19/10 = 1 9/10
3) 6 3/4 - 1 9/10 = 6 15/20 - 1 18/20 = 5 35/20 - 1 18/20 = 4 17/20
4) 4 17/20 + 2/5 = 4 17/20 + 8/20 = 4 25/20 = 4 5/4 = 5 целых 1/4
2) 90х90=810 мм - площадь