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The number of three digit having only two comsecutive digits identical is_______ (A) 153 (B) 162 (C) 180 (D) 161 Please explain step by step.

The number of three digit having only two comsecutive digits identical is_______
(A) 153
(B) 162
(C) 180
(D) 161
Please explain step by step.

Grade:11

1 Answers

Sher Mohammad IIT Delhi
askIITians Faculty 174 Points
8 years ago
two identical digits remain in pair so we can count them as one digit.
Next, both are identical so only one way to represent. first digit can't be zero so 9 choices 10 for other one. and these two can be arranged in two ways.
so 9*10*2=180 ways

Sher Mohammad
Faculty askiitians

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