Question

A letter lock consists of $3$ rings each marked with six different letters. The number of distinct unsuccessful attempts to open the lock is at the most

• A. $215$
• B. $243$
• C. $216$
• D. $244$

Answer 1

Answer: (A)

$215$

Total number of combination of letters of ring $=6\times 6\times 6=216$

But among these 1 would be successful event

Therefore total number of unsuccessful events$=216-1=215$