A “double-single” number is a three-digit number made up of two identical digits followed by a different digit. For example, 553 is a double-single number. How many double-single numbers are there between 100 and 1000?
110 112 113 114 115 116 117 118 119 220 221 223 224 225 226 227 228 229 330 331 332 334 335 336 337 338 339 440 441 442 443 445 446 447 448 449 550 551 552 553 554 556 557 558 559 660 661 662 663 664 665 667 668 669 770 771 772 773 774 775 776 778 779 880 881 882 883 884 885 886 887 889 990 991 992 993 994 995 996 997 998 Total = 81 such numbers
