Question

1-2+3-4+5-6.+1991-1992+1993用简便计算怎么算？

Answer 1

1-2+3-4+5-6.+1991-1992+1993
=1+(3-2)+(5-4)+(7-6)+...+(1993-1992)
=1+1+...+1
=997

Answer 2

1-2+3-4+5-6+……+1991-1992+1993
=1993-1992+1991-1990+……+5-4+3-2+1-0
=(1993-1992)+(1991-1990)+……+(5-4)+(3-2)+(1-0)
=1×{[(1993-0)÷1+1]÷2}
=997

Answer 3

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