Question

how many four digit number are there if repetation of digit is allowed

Answer 1

Answer:

9000

Step-by-step explanation:

Four Digit numbers are

9*10*10*10=9000(if repetition of digits is permitted).Since first digit cannot be zero we have 9 options and other digits can use any number between (0-9)

Answer 2

Step-by-step explanation:

What is the sum of all 4-digit numbers that can be formed using the digits 1,2,3,4 where repetition of digits is allowed? As each digit of four digit number (abcd) can take 4 options (1, 2, 3, 4) total there can be 4^4 numbers.