are possible combinations .
<u>Step-by-step explanation:</u>
Here we have , A laptop lock has a 4 digit combination. Each character can be any digit between 0-7. The only restriction is that all 4 characters cannot be the same (e.g. 0000, 1111, 2222,... etc.). We need to find How many combinations are possible .Let's find out:
The first digit has 8 choices (can be all of them), the second digit also has 8 choices. The third and fourth digits also have 8 choices.
Multiply them together you get:
⇒
⇒ possible combinations.
But since all 4 characters cannot be the same, we subtract 8 from 4096 (there are 8 combinations which the 4 characters are the same: 1111, 2222, 3333, 4444, 5555, 6666, 7777, and 0000) and we get :
⇒
⇒
Therefore, are possible combinations .