Question

The following problem refers to strings in A, B, ..., Z.

How many three-letter strings are there that begin with U

Answer 1

If the string begins with U, only the last to letters of the string will vary: i.e.

UAA, UAB, UAC, ...
UBA, UBB, UBC, ...
...

So the amount of choices for the first character is one, for the second and third characters you have 26 different choices

Answer 2

So you will have

(choices for letter one)*(choices for letter two)*(choices for letter three)

as your number of combinations of three-letter strings beginning with U

Answer 3

You got it?

Answer 4

so 26*26?

Answer 5

thank you sir :)

Answer 6

Yup :)