The number of five digit telephone numbers having at least one of their digits repeated is `90000` b. `100000` c. `30240` d. 69760

Explanation

Number of 5-digit numbers when all the digits are repeated `= 10 x 10 x 10 x 10 x 10`

`= 100000`

Numbers without the repeated digits `= 10 ** 9 ** 8 ** 7 ** 6 = 30240`

Therefore, numbers having at least one of their digits repeated is `= 100000 – 30240 = 69760`