Question

how many numbers can be formed from the digits 1,3,5,9 if repetition of digit is not allowed​

Answer 1

Answer:

Step-by-step explanation:

24

Using permutations and combinations,

4 places to fill thus it is,

4!=4*3*2*1

=24

Thus 24 numbers can be formed.

As all digits are unique answer is 24 4-digit no. Can be formed.

If 3,2,1 digit no. Are also considered,

4digit no.=24

3digit no.=24 as 4*3*2(3spaces 4 numbers)

2digit=12 as 4*3(2 spaces 4 numbers)

1 digit= 4 as 4*1(1 space and 4 numbers)

So,

If only four digit numbers are considered,answer is 24

If all possible numbers are considered,answer is 64.

If there is no limit of digits, answer is infinite.