SOLUTION: 5 wooden blocks numbered 1,2,3,4,5 are placed by a young child in a row. What is the probability that the numbered formed is... 1. Less than 20,000? 2. More than 40,000?

First we will calculate the denominator of the probability for it is the same for both problems.

It is the number of ways to pick 5 things from 5 things and position them. 

Thats "5 Position 5" or 5P5 =  

We must choose the first digit to be 1. Then we have to pick 4 of the
remaining 4 digits and position them

That's "4 position 4" or 

So the probability is 24 out of 120 or 

We must choose the first digit as 4 or 5.  That's 2 ways to pick the
first digit. For each of those 2 ways to pick the first digit, we have 
to pick 4 of the remaining 4 things and position them. So there are 

2*(4P4) = 

So the probability is 48 out of 120 or 

Edwin