求九年级奥数题（高难度）一道

1.1/2+5/6-7/12+9/20-11/30+13/42-15/56
=1/2+(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)
=1/2+1/2+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=1-1/8
=7/8
2.3.14×1.43+62.8×0.331+39×0.157
=0.157×(20×1.43+400×0.331+39)
=0.157×(28.6+132.6+39)
=0.157×200
=31.4
3.139×137/138+137×139/138

=（138+1）×137/138+（138－1）×139/138

=137+137/138+139－139/138

=275+136/138

=275+68/69
给你三个，你慢慢选把，是六年级的。

1.1/2+5/6-7/12+9/20-11/30+13/42-15/56
=1/2+(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)
=1/2+1/2+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=1-1/8
=7/8
2.3.14×1.43+62.8×0.331+39×0.157
=0.157×(20×1.43+400×0.331+39)
=0.157×(28.6+132.6+39)
=0.157×200
=31.4
3.139×137/138+137×139/138

=（138+1）×137/138+（138－1）×139/138

=137