Question

Megan is in charge of creating a five-digit code to lock and unlock a secure room. She can use any digit from 0 through 9, and she can use each digit as many times as she wants. She knows she wants to start the code with a 7.

How many possible codes that start with 7 could Megan create?

Responses

a) 10,000 codes
b) 70,000 codes
c) 70,000 codes
d) 700,000 codes

Answer 1

Answer: a) 10000

Explanation:

The code has five digits, and the first digit is fixed (i.e., it must be 7) so we only care for the other

The second digit has 10 possible options.

The third digit has 10 possible options.

The fourth digit has 10 possible options.

The fifth digit has 10 possible options.

The total number of combinations is given by the product between the number of combinations10

C = 1*10*10*10*10 = 10000 codes.

So, the correct option is first one.