AMC10 2016 A
AMC10 2016 A · Q1
AMC10 2016 A · Q1. It mainly tests Exponents & radicals, Primes & prime factorization.
What is the value of $\dfrac{11!-10!}{9!}$?
$\dfrac{11!-10!}{9!}$ 的值是多少？
(A)
99
99
(B)
100
100
(C)
110
110
(D)
121
121
(E)
132
132
Answer
Correct choice: (B)
正确答案：（B）
Solution
Answer (B):
$\dfrac{11!-10!}{9!}=\dfrac{10!\cdot(11-1)}{9!}=\dfrac{10\cdot9!\cdot10}{9!}=100$
答案（B）：
$\dfrac{11!-10!}{9!}=\dfrac{10!\cdot(11-1)}{9!}=\dfrac{10\cdot9!\cdot10}{9!}=100$
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