Since in a pass code, the placement of the digits is
important, therefore this means that to solve for the total number of
possibilities we have to make use of the principle of Permutation. The formula
for calculating the total number of possibilities using Permutation is given
as:
P = n! / (n – r)!
where,
n = is the total amount of numbers to choose from = 20
r = is the total number of digits needed in the passcode =
4
Therefore solving for the total possibilities P:
P = 20! / (20 – 4)!
P = 20! / 16!
P = 116,280
Hence there are a total of 116,280 possibilities of pass
codes.
