The total number of eight – digit landline telephone numbers that can be formed having at least one of their digits repeated is:
Explanation:
The total number of 8-digit landline telephone numbers that can be formed having at least one of their digits repeated = The total number of 8-digit landline numbers – The number of 8-digit landline numbers in which no digit is repeated.
The total number of 8-digit landline numbers = 108
The number of 8-digit landline numbers in which no digit is repeated = 10!/2
∴ Number of required landline numbers = 98185600
Hence, option (a).
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