Re: An office manager must choose a five-digit lock code for the

An office manager must choose a five-digit lock code for the office door. The first and last digits of the code must be odd, and no repetition of the digits is allowed. How many different lock codes are possible.?


Odd numbers 1,3,5,7,9 so first digit 5 options, last place 4 options ( no repetition).
That leaves us with 7 (of 9) digits to choose for the middle three.

So we have 5 x 4 for the irst and last
and 7 x 6 x 5 for the iddle three
Total is 5 x 7 x 6 x 5 x 4 = 4200.

The book shows 5 x 8 x 7 x 6 x 4= 6720.

I think this is wrong.

Any ideas.