Question

Four letters E, K, S and V, one in each, were purchased from a plastic warehouse. How many ordered pairs of letters, to be used as initials, can be formed from them?

Answer 1

Here, we need to find out the number of pairs of the letters that can be formed with the 4 letters.
Required number of ordered pairs = Number of arrangements of four letters, taken two at a time = ⁴P_{2
$$\begin{gathered} =\frac{4!}{\left(4-2\right)!} \\ =\frac{4!}{2!} \\ =\frac{4\times 3\times 2!}{2!} \\ =4\times 3 \\ =12 \end{gathered}$$}