(1-1/4)=(1+1/2)(1-1/2)=3/2*1/2
(1-1/9)=(1+1/3)(1-1/3)=4/3*2/3
……
(1-1/100)=(1+1/10)(1-1/10)=11/10*9/10
(1-1/4)(1-1/9)(1-1/16)…… (1-1/81)(1-1/100)
=1/2*3/2*2/3*4/3……9/10*11/10
=11/20
(1-1/4)=(1+1/2)(1-1/2)=3/2*1/2
(1-1/9)=(1+1/3)(1-1/3)=4/3*2/3
……
(1-1/100)=(1+1/10)(1-1/10)=11/10*9/10
(1-1/4)(1-1/9)(1-1/16)…… (1-1/81)(1-1/100)
=1/2*3/2*2/3*4/3……9/10*11/10
=11/20