+48 Final Answer:
2880
Reasoning:
Odd numbers: 1,3,5,7,9
Even numbers: 2,4,6,8
So there are 5 odd numbers and 4 even numbers.
| 5 | 4 | 4 | 3 | 3 | 2 | 2 | 1 | 1 |
^ The number possibilities
For the first box, there are five possibilities, because there are five odd numbers.
For the second slot, there are four because there are four even numbers.
For the third, there are four possibilities, because there are four odd numbers left, since you can not use whatever was the first option.
For the fourth slot, there are three possibilities, because there are three even numbers remaining.
The pattern continues, until we are down to the ninth box, the unit digit, where there is only one possibility remaining.
Multiply what you get from the slots:
5*4*4*3*3*2*2*1*1
= 2880
Please reply if you find a mistake lurking!
=^-^=
