Question

A letter lock consists of three rings each marked with $10$ different letters. Find the number of ways in which it is possible to make an unsuccessful attempts to open the lock.

Answer 1

No. of rings in a lock $=3$

No. of different letters $=10$

$\therefore$ Total No. of attempts $=(10\times 10\times 10)=1000$

No. of successful attempts $=1$

$\therefore$ Total No. of unsuccessful attempt $=(1000-1)=999$ attempts