4/5÷9右4/5÷99右4/5÷999右4/5÷9999右4/5=(5-1)/5x5/(50-1)x5/(500-1)x5/(5000-1)x5/(50000-1)=(5-1)x5/(50-1)(50000-1)x25/(500-1)(5000-1)=20/(2500000-50000-50+1)x25/(2500000-5000-500+1)=500/［(2450000-49...