Answer :
Answer:
432
Step-by-step explanation:
We are given that a four digit number can be formed by using digits from 1 to 9.
Two digits equal to each other and other two digits are equal to each other .
We have to find number of four digit numbers can be formed using digits from 1 to 9.
Total digits =9
Number of ways to filled first place =9
Number of ways to filled second place =1 because two digits are same
Number of ways to fill the third place =8 because different from previous two digits
Number of ways to fill the fourth place =1 because remaining two digits are same
Total number of ways to make four digit number =[tex]9\times 1\times 8\times 1\times {\frac{4!}{2!2!}}[/tex]
Because two digits out of 4 and remaining two digits are same select out of 4
Total number of ways in which four digit number can be formed=[tex]9\times 8\times 3\times 2=432[/tex]