900:9+1 = (100+10+1)+1 = 111+1 = 1129000:91 = (1000+100+10)1 = 11101 = 111090000:9:1 = (10000+1000+100)1 = 11100.
900:9+1 = (100+10+1)+1 = 111+1 = 112
9000:91 = (1000+100+10)1 = 11101 = 1110
90000:9:1 = (10000+1000+100)1 = 11100.