How many three digit numbers can having only two consecutive digits identical is

(a) 153 (b) 162 (c) 168 (d) 163 (e) None of these

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1 Answers

(b) When 0 is the repeated digit like
100, 200, ...., 9 in number
When 0 occurs only once like
110, 220, ....., 9 in number
When 0 does not occur like
112, 211, ....., 2 × (8 × 9) = 144 in number.
Hence, total = 9 + 9 + 144 = 162.

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