How many one-to-one functions are there from the set {A, B, C} to the set {x, y, z, t, w, k}?

A one-to-one function means that each element from the domain can be mapped into only one element from the range (like for a typical function), and each element from the range can be mapped only once.

This means that, for two different inputs x₁ and x₂, we can't have:

f(x₁) = f(x₂)

Because that would mean that two different values of the domain are being mapped into the same element from the range.

Ok, now that we know this, let's count the number of possible "mappings" for each element in the domain.

For the first element, A, we have the options {x, y, z, t, w, k} (a total of 6 options).

For the second element, B, we will have an option less (because one was already taken) so here we have 5 options.

For the last element on the domain, C, there will be again an option less than in the previous case, so here we have 4 options.

The total number of combinations (each combination defines a different one-to-one function) is equal to the product between all the options for each case, then the total number of one-to-one functions is:

C = 6*5*4 = 120

There are 120 different one-to-one functions.