Question

A suitcase has a lock on it consisting of three numbers. Each number could be any
number 0-9. The only restriction is that two numbers in a row cannot be the same
(e.g. you couldn’t use 322 because the 2’s are adjacent but you could use 343
since none of the same numbers are adjacent).

Answer 1

Answer:

810

i hope I'm right.

Step-by-step explanation:

there are 10 digits and 3 places to be filled.

the first place can be any of the 10 digits.

so 1st place possibilities=10

the second place can be any of the 10 digits except the one used in the first place, as per condition.

so 2nd place possibilities=9

the third place can be any of the 10 digits, even the one used in the first place but not the one used in the 2nd place.

so 3rd place possibilities=9

no. of possibilities = 10×9×9

=810