六年级数学题能简算的要简算
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六年级数学题能简算的要简算
六年级数学题能简算的要简算
六年级数学题能简算的要简算
1/2+1/6+1/12+1/20+1/30
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6
=1-1/6
=5/6
裂项。
看这里:http://zhidao.baidu.com/question/540553215.html
拆分。
1/2+1/6+1/12+1/20+1/30
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6
=1-1/6
=5/6