公务员数学运算题一道

求详解过程

2024-12-14 06:52:55

推荐回答（1个）

回答1：

D.11/45

1/(1×2×3)=[1/(1×2)-1/(2×3)]/2
1/(2×3×4)=[1/(2×3)-1/(2×3)]/2
1/(3×4×5)=[1/(3×4)-1/(4×5)]/2
1/(4×5×6)=[1/(4×5)-1/(5×6)]/2
.................................
1/(8×9×10)=[1/(8×9)-1/(9×10)]/咐举2

所以
1/(1×2×3)+1/(2×3×4)+…+1/（8×9×10）
=[1/(1×2)-1/(2×3)]/2+[1/(2×3)-1/(2×3)]/2+[1/(3×4)-1/(4×5)]/2+[1/(4×5)-1/(5×6)]/2+...+[1/(8×9)-1/(9×10)]/2
=[1/(1×2)-1/(2×3)+1/(2×3)-1/(2×3)+1/(2×3)-1/(2×3)+1/衡源碧(3×4)-1/(4×5)+1/(4×5)-1/(5×6)+...+1/(8×9)-1/(9×10)]/2
=[1/(1×2)-1/(9×10)]/2
=(1/2-1/90)/2
=(44/90)/2
=22/90
=11/裂伍45