Question

A letter lock consists of three rings each narked with 10 different letters. In how many nays it is possible to make an unsuccessful attempt to open the lock ?

Answer 1

The total number of ways to make ttempt to open the lock = $10\times 10\times 10=1000$. The number of ways to successfuly open the lock = 1 $\therefore$ The number of ways to make an nsuccessful attempt to open the lock = 1000 -1 = 999. Hence, required number of ways to make an unsuccessfuly attempt to open the lock is 999.