(1-3/8)x(1-3/15)x(1-3/24)x⋯x（1－ 3/99)=5/8×12/15×21/24×32/35×45/48×60/63×77/80×96/99=(5×12×21×32×45×60×77×96)/(8×15×24×35×48×63×80×99)=1/3约分后等于3分之1
