Question

小学六年级数学 用简便方法计算1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72

Answer 1

原式=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+1/8-1/9
=1-1/9
=8/9

Answer 2

1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
=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+1/8-1/9
=1-1/9
=8/9

Answer 3

解 原式=1/1×2+1/2×3+1/3×4+······+1/7×8+1/8×9
=1/1-1/2+1/2-1/3+1/3-1/4+······+1/7-1/8+1/8-1/9
=1/1-1/9
=8/9

Answer 4

1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
=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+1/8-1/9
=1-1/9
=8/9

Answer 5

1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
=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+1/8-1/9
=1-1/9
=8/9

Answer 6

1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
= 1-1/2 + 1/2 - 1/3 + 1/3 - 1/4 +...+ 1/8 - 1/9
= 1 - 1/9
= 8 / 9