A serial number for a computer consists of 4 letters, followed by 5 digits. The letters O, I and Q are not used. How many serial numbers are there if: A. Letters can be repeated but digits cannot be repeated? B. Digits can be repeated but letters cannot be repeated? C. Both letters and digits can be repeated? D. Neither letters nor digits can be repeated?

Answer rating: 100% (QA)

There are 26 alphabets O I Q these three letters are not used So alphabets used26323 There are 10 d... View the full answer