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5 votes
Calculate.
12C4
Note: Cr=
n
n!
r!(n−r)!

User Shshaw
by
8.4k points

1 Answer

3 votes

Answer:

495

Explanation:

using the definition

n
C_(r) =
(n!)/(r!(n-r)!)

where n! = n(n - 1)(n - 2) ... × 3 × 2 × 1

then

12
C_(4)

=
(12!)/(4!(12-4)!)

=
(12!)/(4!(8!))

cancel 8! on numerator/ denominator

=
(12(11)(10)(9))/(4!)

=
(11880)/(4(3)(2)(1))

=
(11880)/(24)

= 495

User Frederic Morin
by
8.2k points