Answer:
Step-by-step explanation:
This is a problem that is sometimes referred to as "n choose k" -- meaning, you have some number to choose from, n, and you have k spots to choose for.
The general formula is: n! / k(n-k)!
Where n = the total number and k = the number chosen.
Here, n = 9 and k = 2.
So, 9! / 2*(9-2)!
(The exclamation point here means factorial, and a factorial is a word meaning to multiply each number below a number and including itself together.)
So, 2! = 2*1 = 2
3! = 3*2*1 = 6
4! = 4*3*2*1 = 24, and so on.
With this problem,
= 362880/2*5040
= 362880 / 10080
= 36
So, there are 36 possible combinations.
