10 ile 99 arasında 90 tane iki basamaklı sayı vardır. İki basamaklı sayılar: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19; 20, 21, 22, 23, 24, 25, 26, 27, 28, 29; 30, 31, 32, 33, 34, 35, 36, 37, 38, 39; 40, 41, 42, 43, 44, 45, 46, 47, 48, 49; 50, 51, 52, 53, 54, 55, 56, 57, 58, 59; 60, 61, 62, 63, 64, 65, 66, 67, 68, 69; 70, 71, 72, 73, 74, 75, 76, 77, 78, 79; 80, 81, 82, 83, 84, 85, 86, 87, 88, 89; 90, 91, 92, 93, 94, 95, 96, 97, 98, 99.