Question

Say that a referral code is 2 letters (A-Z, no lowercases) followed by 4 digits (0-9), or it is 2 digits (0-9) followed by four letters (A-Z, no lowercases). Digits are not allowed to repeat but letters can repeat. How many referral codes can you make

Answer 1

Answer:

Step-by-step explanation:

Given that a referral code is 2 letters (A-Z, no lowercases) followed by 4 digits (0-9), or it is 2 digits (0-9) followed by four letters (A-Z, no lowercases).

Digits are not allowed to repeat but letters can repeat.

Thus we find that 2 letters can be selected in

$26^2 ways$

Since for numbers repitition is not allowed, 4 digits can be arranged in 9P4 ways

= 9*8*7*6

Total no of ways for I type=$26^2*9*8*7*6$

For II type numbers are 2 and letters are 4.

So no of ways = $9P2 *26^4$

total referral codes possible =

$26^2*9*8*7*6+26^4 *9*8\\= 26^2 (9)(8) [42+676]\\= 34946496$