奥数计算题,简便计算1 1 1 1 1 1 ---- + --- + --- +… --- + --- --- 6 12
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/19 12:02:13
奥数计算题,简便计算
1 1 1 1 1 1
---- + --- + --- +… --- + --- ---
6 12 20 72 90 110
1 1 1 1 1 1
---- + --- + --- +… --- + --- ---
6 12 20 72 90 110
1/6=1/(2×3)=1/2-1/3
1/12=1/(3×4)=1/3-1/4
1/20=1/(4×5)=1/4-1/5
……
1/72=1/(8×9)=1/8-1/9
1/90=1/(9×10)=1/9-1/10
1/110=1/(10×11)=1/10-1/11
∴原式=1/(2×3)+1/(3×4)+1/(4×5)+……+1/(8×9)+1/(9×10)+1/(10×11)
=1/2-1/3+1/3-1/4+1/4-1/5+……+1/8-1/9+1/9-1/10+1/10-1/11
=1/2-1/11=9/22
1/12=1/(3×4)=1/3-1/4
1/20=1/(4×5)=1/4-1/5
……
1/72=1/(8×9)=1/8-1/9
1/90=1/(9×10)=1/9-1/10
1/110=1/(10×11)=1/10-1/11
∴原式=1/(2×3)+1/(3×4)+1/(4×5)+……+1/(8×9)+1/(9×10)+1/(10×11)
=1/2-1/3+1/3-1/4+1/4-1/5+……+1/8-1/9+1/9-1/10+1/10-1/11
=1/2-1/11=9/22
奥数计算题,简便计算1 1 1 1 1 1 ---- + --- + --- +… --- + --- --- 6 12
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