Question

Find the number of $5$ digits telephone having atleast one of their digits repeated .(Note . 0 can be accepted in first place )

Answer 1

Number of numbers with repetition$=10\times 10\times 10\times 10\times 10=100000$

Number of numbers without repetition$=10\times 9\times 8\times 7\times 6=302400$

$\therefore$ Number of numbers with atleast one digit repeated$=100000-302400=69760$