Problema Solution
Jill forgot her lock combination. She knows that no digits repeat and there are 4 numbers. How many possible combinations are there for her lock?
Answer provided by our tutors
we need to find the number of possible permutations of k objects from a set of n. This is usually written nPk = n!/(n - k)!
in our case n = 10 and k = 4
10P4 = 10!/(10 - 4)!
10P4 = 7*8*9*10
10P4 = 5040
there are 5040 possible combinations.