Question

Aflați câte nr de trei cifre au exact 2 cifre identice,care sunt acestea?

Answer 1

100,101,110,112,113,114,115,116,117,118,119,121,122,131,133,141,144,151,155,161,166,171,177,181,188,191,199 De la 100 la 200= 27 nr De la 200 la 300=27 nr 300-400=27 400-500=27.....si tot asa pana la 1000 27•9= 243 nr care au exact 2 cifre identice .