Question 1000955
The problem goes like this: 
There are 10 detergent brands that are to be ranked. Determine the probability that 
a.) brand A is ranked first and 
b.) that brand A is in the top 3 brands.
 
I know that the answer to the first is .10, because each of the brands have 1/10 probability of ranking first. 
I'm not sure how to solve for b.) 
An explanation would be great with the solution.
# of ways for brand A to be in the top 3:: 3*9!
-----
# of random arrangements; 10!
-----
P(A in top 3) = 3*9!/10! = 3/10
---------
Cheers,
Stan H.s