We have to evaluate the expression 9C3
Solution
To evaluate the expression 9C3 we use the following formula
nCr =n! / r! (n – r)!
n = 9
r = 3
Substitute n and r values in above formula
nCr =n! / 3! (n – r)!
9C3= 9! / 3! (9-3)!
9C3= 9! / 3! (6)!
Find the factorial for 9!, 3! & 6!, substitute the corresponding values in the below expression and simplify.
= 9 X 8 X 7 X 6 X 5 X 4 X 3 X 2 X 1 / (3 X2 X 1) (6 X 5 X 4 X3 X 2 X 1)
=362880/ (6 ) (720)
= 362880 / 4320
= 84
9C3= 84
Answer
9C3= 84
