The number of five-digit telephone numbers having atleast one of their digits repeated is ( 00000 is also a telephone number)

Step-by-step solution

Number of all five digit sequences (telephone numbers) is 10 × 10 × 10 × 10 × 10 = 10 5 When no digit is repeated, then 10 × 9 × 8 × 7 × 6 = 30240 ⇒ The required number wen atleast one digit is repeated = 100000 - 30240 = 69760