The no of 3 digit nos. having only two consecutive digits identical is?

Dear jee king

identical digits can be at 100th and 10th position  or at 10th and unit place

case 1

  identical digit at 100th and 10th posiition

  0 can be at 100th position so these 2 position can be filled by 9 ways

and unit place can be filled by 9 ways

 total ways =9*9 =81

case 2

identicle digit at 10 th and unit position

 total ways =9*9 =81

 

so total ways =81+81 =162

 

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