小学六年级数学,1/2+1/6+1/12+1/20+1/30+1/42+1/56的简便计算方法,2
小学六年级数学,1/2+1/6+1/12+1/20+1/30+1/42+1/56的简便计算方法,2015*8/2014点方法。...
小学六年级数学,1/2+1/6+1/12+1/20+1/30+1/42+1/56的简便计算方法,2015*8/2014点方法。
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1/2+1/6+1/12+1/20+1/30+1/42+1/56
=1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/x6x7+1/7x8
=(1-1/2)+(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.
考点:单位分数的分拆
1/n(n+1)=(1/n)-(1/n+1))
1/n(n+2)=(1/2)[(1/n)-(1/n+2)]
1/n(n+3)=(1/3)[(1/n)-(1/n+3)]
.....................................
=1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/x6x7+1/7x8
=(1-1/2)+(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.
考点:单位分数的分拆
1/n(n+1)=(1/n)-(1/n+1))
1/n(n+2)=(1/2)[(1/n)-(1/n+2)]
1/n(n+3)=(1/3)[(1/n)-(1/n+3)]
.....................................
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1/2+1/6+1/12+1/20+1/30+1/42+1/56
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)
=1-1/2+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
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)
=1-1/2+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
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1/2+1/6+1/12+1/20+1/30+1/42+1/56
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)
=1-1/2+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
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)
=1-1/2+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
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