Question

Quantos números de 3 algarismos diferentes podemos escrever com os algarismos 1 ao 9

Answer 1

123,124,125,126,127,128,129,132,134,135,136,137,138,139,142,143,145,146,147,148,149,152,153,154,155,156,157,158,159,162,163,164,165,166,167,168,169,172,173,174,175,176,177,178,179,182,183,184,185,186,187,188,189,192,193,194,195,196,197,198,199
213, 214,215 216,217,218,219,etc