Question

The number of $5$ digit telephone numbers having least one of their digits repeated is

• A. $90,000$
• B. $100,000$
• C. $30,240$
• D. $69,760$

Answer 1

The correct option is D $69,760$

Consider the given question,

Numbers with repetition$=10\times 10\times 10\times 10\times 10$

$=1,00,000$

Numbers without repetition $=10\times 9\times 8\times 7\times 6$

$=30240$

Number with one digit is repeated$=100000-30240$

$=69760$

Hence, the number of 5 digit telephone numbers having least one of their digits repeated is $69760$