1/2+5/6+11/12+19/20+29/30+41/42简便算法
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1/2+5/6+11/12+19/20+29/30+41/42简便算法
1/2+5/6+11/12+19/20+29/30+41/42简便算法
1/2+5/6+11/12+19/20+29/30+41/42简便算法
每个加数都写成(1-一个数)
原式=6-(1/2+1/6+1/12+...1/42)
1/6=1/2-1/3 1/12=1/3-1/4 ... 1/42=1/6-1/7
1/2+1-1/6+1-1/12+1-1/20+1-1/30+1-1/42=1/2+5-1/6-1/12-1/20-1/30-1/42=1/2+5-(1/6+1/12+1/20+1/30+1/42)=1/2+5-(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6-1/6-1/7)=1/2+5-(1/2-1/7)=1/2+5-1/2+1/7=5+1/7=5又1/7
如果有的话先是将分子大的化小,如
29/30=1-1/30然后把有公约数的相组合,如1/6,1/42相加减,最后是全部相加减
1/2+5/6+11/12+19/20+29/30+41/42
=1-1/2+1-1/6+1-1/12+.....+1-1/42
=6-(1/2+1/6+1/12+1/20+1/30+1/42)
=6-(1-1/2+1/2-1/3+1/3-1/4+.....+1/6-1/7)
=6-(1-1/7)
=6-6/7
=5又6/7
1/2+5/6+11/12+19/20+29/30+41/42
=1-1/2+1-/6+1-1/12+1-1/20+1-1/30+1-1/42
=6-(1/2+1/6+1/12+1/20+1/30+1/42)
=6-(1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7)
=6-(1/2+1/2-1/7)
=5+1/7
=36/7