Question

Câte numere naturale de trei cifre știind ca prima și ultima cifra sunt identice?

Answer 1

101,111,121,131,141,151,161,171,181,191,202,212,222,232,242,252,262,272,282,292,303,313,323,333,343,353,363,373,383,393,404,414,424,434,444,454,464,474,484,494,505,515,525,535,545,555,565,575,585,595,606,616,626,636,646,656,666,676,686,696,707,717,727,737,747,757,767,777,787,797,808,818,828,838,848,858,868,878,888,898,909,919,929,939,949,959,969,979,989,999.

Answer 2

pe prima si pe ultima pozitie avem 9 posibilitati, iar la mijloc 10 posibilitati, in total avem 10*9=90 numere:
101,111,121,...191
202,212,222,...292
...
...
909, 919,929,..999