\frac{9}{10}
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Express the following sum as a common fraction: $$\frac{1}{1\cdot 2} + \frac{1}{2\cdot 3} + \frac{1}{3\cdot 4} + \frac{1}{4\cdot 5} + \dots + \frac{1}{9\cdot 10}$$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\frac{9}{10}
Express the following sum as a common fraction: $$\frac{1}{1\cdot 2} + \frac{1}{2\cdot 3} + \frac{1}{3\cdot 4} + \frac{1}{4\cdot 5} + \dots + \frac{1}{9\cdot 10}$$
train