Gaokao Math Practice Question
已知等差数列 $\left\{a_{n}\right\}$ 的前 $n$ 项和为 $S_{n}, a_{5}=5, S_{5}=15$, 则数列 $\left\{\frac{1}{a_{n} a_{n+1}}\right\}$ 的前 100 项和为 ($\qquad$)
- A.$\frac{100}{101}$
- B.$\frac{99}{101}$
- C.$\frac{99}{100}$
- D.$\frac{101}{100}$
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