Question

an internet passcode consists of a digit followed by a letter, followed by another digit. Assuming the digits are 0-9, how many different passcode are possible?

Answer 1

There are 10 single-digits (0 through 9) and 26 letters (A through Z)

For the first slot there are 10 choices which represents selecting a single digit
For the second slot there are 26 choices because we choose a single letter here.
Finally there are another 10 choices for the third slot (assuming repeats are allowed)

Multiply the values out: 10*26*10 = 260*10 = 2600

Answer: 2600