1-1/2-1/20-1/200-1/2000-1/20000

如果一个数列从第2项起，每一项与它的前一项的比等于同一个常数，这个数列就叫做等比数列。这个常数叫做等比数列的公比，公比通常用字母q表示。Sn=A1(1-q^n)/(1-q)
原式=1-1/2×(1-1/10的5次方)/(1-1/10)
=1-11111/20000
=8889/20000

1 - (1 / 2) - (1 / 20) - (1 / 200) - (1 / 2 000) - (1 / 20 000)
= 0.44445

=（20000-10000-1000-100-10-1）/20000
=（20000-11111）/20000
=8889/20000

原式=1-(1/2+1/20+1/200+1/2000+1/20000)
=1-(1/2-1/200000)/(1-1/10)
=1-11111/20000
=8889/20000
等比公式

等比数列
1-1/2×（1+1/10+1/100+1/1000+1/10000）
=1-1/2×((1-(1/10)^5)/(1-1/10))
=1-1/2×99999/100000×10/9
=1-1/2×11111/10000
=9999/20000

1-1/2-1/20-1/200-1/2000-1/20000
=1-0.5-0.05-0.005-0.0005-0.00005
=0.44445