Question

How many different positive integers of 2 digits each can be made with the digits 2, 4, 5, and 8, if no digit is repeated in a number? 8 12 16

Answer 1

12 different positive integers can be written.
24
25
28
42
45
48
52
54
58
82
84
85

Answer 2

Answer: 12

Explanation:

Given : The total number digits given : 4

Since repetition is not allowed then to find the number of different positive integers of 2 digits each can be made with the digits 2, 4, 5, and 8 we use permutations.

We know that the permutation of n things taking m at a time is given by :-

`^nP_m=(n!)/((n-m)!)`

Similarly, the number of permutations of 4 things taking 2 at a time is given by :-

`^4P_2=(4!)/((4-2)!)\\\\=(4*3*2!)/(2!)=12`

Hence, the required number of different positive integers = 12.