1+2+3.1990=?7又8/9+33+7.5-3.7-4又2/9-2.8=?385x(-125)x(-11)x8x1/25x(-5/11)=?把你会回答的写出来

Question

1+2+3.1990=?7又8/9+33+7.5-3.7-4又2/9-2.8=?385x(-125)x(-11)x8x1/25x(-5/11)=?把你会回答的写出来

Answer 1

1 + 2 + 3 + ...+ 1990 = (1 + 1990) * 1990 / 2 = 1981045
.
.7又8/9+33+7.5-3.7-4又2/9-2.8
.=71/9 + 33 + 7.5 - 3.7 - 38/9 - 2.8
.=(71/9 - 38/9) + 33 + (7.5 - 3.7 - 2.8)
.=11/3 + 33 + 1
.113 2
.= ----- = 37---
.2 3
.
.385x(-125)x(-11)x8x1/25x(-5/11)
.= -385 * (11 * 5/11) * (8 * 125 * 1/25)
.= -385 * 5 * 40
.= -77000
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大锅别这么懒行不,这题不难的