简便计算,各位哥哥姐姐急啊!1.1/2+1/6+1/12+……+1/902.1999÷1998/19993.246×321963/1233694.14.8×6.3+46.5×4.5+8.3×3.7+0.465×550-6.3×6.5

Question

简便计算,各位哥哥姐姐急啊!
1.1/2+1/6+1/12+……+1/90
2.1999÷1998/1999
3.246×321963/123369
4.14.8×6.3+46.5×4.5+8.3×3.7+0.465×550-6.3×6.5

Answer 1

1.1/2+1/6+1/12+……+1/90
=(1-1/2)+(1/2-1/3)+……+(1/9-1/10)
=1-1/10
=9/10
2.1999÷1998/1999
=1999×1999/1998
=1999×(1998+1)/1998
=1999×1998/1998+1999*1/1998
=1999+1999/1998
=2000又1/1998
3.246×321963/123369
=246×321×1003÷(1003×123)
=321×2
=642
4.14.8×6.3+46.5×4.5+8.3×3.7+0.465×550-6.3×6.5
=6.3×（14.8－6.5）+46.5×（4.5+5.5）+8.3×3.7
=6.3×8.3+46.5×10+8.3×3.7
=8.3×(3.7+6.3)+465
=8.3×10+465
=83+465
=548