Question

There are 9 balls in a hat .The balls are numbered 1-9 you need to choose 3 of the balls . How many possible combinations are there

Answer 1

84

Explanation:

Combinations

nCr

n (objects) = 9

r (sample) = 3

9C3

n! / r! (n – r)!

9! / 3! (9 – 3)!=

9! / (3! * 6!)=

9*8*7*6!/ (3! * 6!)=

6! cancels out

9*8*7/3*2*1=

3*4*7=

12*7=

84