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How many three-digit passwords are possible on a home

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by BTGmoderatorLU » Sat Mar 31, 2018 2:27 pm
How many three-digit passwords are possible on a home security system keypad that consists of all the digits?

A. 10^3
B. 900
C. 26^3
D. 26*25*25
E. 10*9*8

The OA is A.

The question says it has to be a three-digit number, so should not the first digit just have 9 option than 10?

Likewise, I got 9*10*10 = 900 as the answer.

Can anyone please explain where did I go wrong? Thanks in advance.
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by ErikaPrepScholar » Sat Mar 31, 2018 3:05 pm
Three-digit passwords can begin with 0. So options like 011, 076, 002, and 000 are all valid passwords. This gives 10 options for each digit, or 10*10*10=10^3 possibilities in total.
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by Jeff@TargetTestPrep » Sat Jul 14, 2018 9:57 am
BTGmoderatorLU wrote:How many three-digit passwords are possible on a home security system keypad that consists of all the digits?

A. 10^3
B. 900
C. 26^3
D. 26*25*25
E. 10*9*8
There are ten 1-digit numbers, including 0. Thus, the number of possible 3-digit passwords is 10 x 10 x 10 = 10^3.

Answer: A

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