Sebuah kode terdiri dari empat digit angka berbeda. Jika angka yang digunakan 1-9 , banyak kode yang mungkin dibuat adalah...

<p> The question is asking for the number of different codes that can be created using four distinct digits from the numbers 1-9. This is a permutation problem since the order of the digits matters in codes. No digit can be repeated as the problem specifies that they should be different. The solution involves calculating the number of ways to choose 4 different digits from 9 and then arranging those in all possible orders. The formula for permutation of choosing r elements from a set of n elements is nPr = n! / (n-r)!, where "!" denotes factorial, which is the product of all positive integers up to that number. Therefore, the number of codes can be calculated using the permutation formula with n=9 (digits available) and r=4 (digits to be chosen for the code).<br /><br />nPr = 9P4 = 9! / (9-4)! = 9! / 5! <br /><br />Further calculation then gives the total number of possible codes as follows:<br /><br />9! / 5! = 9*8*7*6*5! / 5! = 9*8*7*6<br /><br />By solving 9*8*7*6, we obtain the number of possible 4-digit codes that can be made with the digits 1-9.</p>