10 choose 5

解答

10 C 5

252

求解步骤

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

代入

n = 10, r = 5

= \frac{10 !}{5 ! ( 10 - 5 ) !}

\frac{10 !}{5 ! ( 10 - 5 ) !} = 252

= 252

a r i t hm e t i c m e an 9, 6, 9, 3, 5, 9, 6, 9, 4, 3, 9, 9, 5, 9, 6, 7, 7, 8, 8, 3

a r i t hm e t i c m e an 48, 42, 56, 64, 40, 40, 48, 42, 56, 30, 64, 48, 53

g eo m e t r i c m e an 90, 94, 53, 68, 79, 84, 87, 72, 70, 69, 65, 89, 85

6 C 2

7 c 2