JEE MAIN - Mathematics (2022 - 25th June Evening Shift - No. 21)
The total number of three-digit numbers, with one digit repeated exactly two times, is ______________.
Answer
243
Explanation
$$C - 1:$$ All digits are non-zero
$${}^9{C_2}\,.\,2\,.\,{{3!} \over 2} = 216$$
$$C - 2$$ : One digit is 0
$$0,\,0,\,x \Rightarrow {}^9{C_1}\,.\,1 = 9$$
$$0,x,\,x \Rightarrow {}^9{C_1}\,.\,2 = 18$$
Total $$ = 216 + 27 = 243$$
Comments (0)
