Q47 / 160 · AP EAMCET 2005 · Mathematics

A three digit number $n$ is such that the last two digits of it are equal and differ from the first. The number of such $n$ 's is

  • A
    64
  • B
    72
  • Correct answer
    C
    81
  • D
    900

Solution

If the last two digits is 0,0 , then in Ist digit any of the numbers except 0 i.e., 9 numbers If the last two digits is 1,1 , then in Ist digit any of the numbers except 0 and 1 , i.e. 8 numbers $\therefore$ The total number of numbers $=9+8 \times 9=81$

Hence, the correct answer is option: 'C'.

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