C(15,3)

解答

C (15, 3)

455

求解步骤

= \frac{n !}{r ! ( n - r ) !}

代入

n = 15, r = 3

= \frac{15 !}{3 ! ( 15 - 3 ) !}

\frac{15 !}{3 ! ( 15 - 3 ) !} = 455

= 455

s t d 13, 14, 32, 53, 53, 53, 58, 64, 65, 67, 69, 69, 70, 72, 73

12 c 4

15 c 4

g eo m e t r i c m e an 320, 135

a r i t hm e t i c m e an 1.2, 1.4, 1.6, 1.8, 2