How many four-digit positive integers can be formed by using the digits from 1 to 9 so that two digits are equal to each other a
1 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 =
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=
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