Question

a customer forgets a 4 digit code for an ATM in a bank. However he remembers that this code consists od 3,5,6 and 9. Find the largest possible number of trails necessary to obtain the correct code?

Answer 1

4×3×2×1=24

If you need further explanation, pls comment

Answer 2

Answer:

the possible number of trails =  24

Step-by-step explanation:

Let the four digit ATM pin be A B C D

Now ,

Since he remembers there are 3, 5, 6 and 9 in this code

So, A B C D will contain all four distinct digit among 3, 5, 6, 9

Now,

For position of A there are all the four possibilities , that is,

A can have any of the 4 digits

Since position of A is filled now,

For position of B there are there possibilities , that is,

B can have 3 digits

Since positions of A and B are  filled now,

For position of C there are two possibilities , that is,

C can have 2 digits

Since positions of A, b and C are all filled now,

For position of D there is only digit left

so, D can have 1 digit that is left out

⇒ A   B   C   D

    4 * 3 * 2 * 1

So the possible number of trails = 4*3*2*1 = 24